Assembly for percutaneously inserting an implantable medical device, steering the device to a target location and deploying the device

ABSTRACT

An assembly for implanting a medical device such as an electrode array. The assembly includes a sheath that is disposed over the medical device and a core that supports the device. The sheath and core are connected to, respectively, first and second slides in a handpiece. An single actuator first moves one slide, typically the slide to which the sheath is attached. Once the first slide at least partially displaced both slides are moved to simultaneously retract the sheath and core away from the implantable medical device. The assembly includes a steering assembly for steering the sheath and implantable medical device. Some of the components forming the steering assembly are disposed on at least one of the slides. Tensioners prevent the steering cables of the steering assembly from being exposed to excessive force.

RELATIONSHIP TO PRIORITY APPLICATIONS

This application is a continuation of PCT Pat. App. No.PCT/US2012/039130 filed 23 May 2012. PCT Pat. App. No. PCT/US2012/039130is a non-provisional of U.S. Prov. Pat. App. No. 61/490,876 filed 27 May2011. The priority applications are specifically incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates generally to a system and method forpercutaneously inserting and deploying an implantable medical devicearray. More particularly, the system of this invention is able to insertthe device in a minimally invasive procedure, steer the device to atarget location and then, if appropriate unfold the device.

BACKGROUND OF THE INVENTION

There are a number of medical conditions for which it has been foundthat an effective therapy involves driving current through a section ofthe tissue of a patient. Often, the current is driven between theelectrodes of an electrode array implanted in the patient. Generally,the electrode array includes a non-conductive carrier on which typicallytwo or more electrodes are disposed. Once the electrode array isimplanted, current is driven from at least one of the electrodes,through the adjacent tissue, to at least one of the other electrodes.The current flow through the tissue influences the tissue to accomplisha desired therapeutic result. For example, an electrode array positionedadjacent the heart may flow currents to stimulate the appropriatecontraction and expansion of the heart muscles. There is an increasinginterest in implanting electrode arrays adjacent neural tissue so thatthe resultant current flow induces a desired neurological or physicaleffect. In one known application, the current driven between theelectrodes of an array placed on top of the dura in the vertebral columnreduces the extent to which chronic pain signals are perceived by thebrain. Alternatively, the array may be placed in a location where thecurrent flow stimulates a feeling of stomach fullness as part of anappetite suppression/weight management therapy. In another application,the current is flowed to tissue or nerves associated with the bladder orthe anal sphincter to assist in control of incontinence. Electrodes maybe implanted in a paralysis victim to provide muscle control and/or asense of feeling.

The Applicants' Patent Application No. PCT/US2009/33769, FOLDABLE,IMPLANTABLE ELECTRODE ARRAY ASSEMBLY AND TOOL FOR IMPLANTING SAME, filed11 Feb. 2009, published as WO 2009/111142 and as U.S. Pat. Pub. No. US2011/0077660 A1, the contents of which are explicitly incorporatedherein by reference, describes an electrode array that includes a frameon which plural electrodes are arranged in a row by column matrix. Anadvantage of this electrode array is that it allows current to be flowedbetween numerous different combinations of electrodes. Depending onwhich electrodes are operated to function as current sources and sinks,this array can be operated so that there are two or more current flowsoccurring simultaneously between different sets of electrodes. Once thisarray is deployed, the practitioner drives current between differentcombinations of electrodes. Current therefore flows through differentsections of tissue. This allows the practitioner to determine betweenwhich electrodes, through which tissue, the current flow offers thegreatest benefit and/or tolerable side effects. Once the optimal currentflow path between the electrodes is determined, the array and itsassociated power supply are set to operate in this state. Should theelectrodes shift or the clinical needs change, the array can be reset toaccommodate these changes.

In comparison to other electrode arrays with lesser numbers ofelectrodes, the above-described array makes it possible to flow currentthrough more discretely targeted sections of tissue and to selectivelyfocus/diffuse the current flow. In contrast to an electrode array with asmaller number of electrodes, use of the above-described array increasesthe likelihood that the current flow can be set to provide desiredtherapeutic effects, with tolerable side effects.

Previously, there was a disadvantage of providing an electrode arraywith numerous individual electrodes that collectively occupy a largesurface area. Specifically, owing to the size of these arrays, it wasbelieved that the only way to position them against the tissue throughwhich current is to be driven was to cut a relatively large incision inthe patient to provide access to the target tissue. Typically, thisincision is more than 3 cm in length and, often at least 5 cm in length.Once the incision is made, it is then usually necessary to retract atleast a portion of the tissue overlying the target tissue. In someinsertion procedures, removal of some of the overlying tissue isrequired. The electrode array was passed through the incision and placedagainst the target tissue. Once the electrode array was positioned, theincision was closed.

The electrode array of the incorporated by reference WO 2009/111142, isdesigned in part to be implanted in a patient without requiring such alarge sized incision, tissue removal and the attendant trauma thatresults from these procedures. The Applicants' array of thisincorporated-by-reference document is designed so that the electrodesare disposed on a frame formed from a superelastic material. Asuperelastic material is one that, after being subjected to appreciablebending or folding, returns to its initial state. Once this electrodearray is formed, the assembly is then folded or rolled into a form thathas a side-to-side width appreciably less than its width in theunfolded/unrolled state.

The Applicant's PCT Pat. App. No. PCT No. PCT/US2010/029628, publishedas US 2012/0022551 A1, DELIVERY ASSEMBLY FOR PERCUTANEOUSLY DELIVERINGAND DEPLOYING AN ELECTRODE ARRAY AT A TARGET LOCATION, THE ASSEMBLYCAPABLE OF STEERING THE ELECTRODE ARRAY TO THE TARGET LOCATION, filed 1Apr. 2010, the contents of which are incorporated herein by reference,discloses how a foldable electrode array can be folded around a core.The core and folded over array are encased in a sheath. Steering cablesare encased in the sheath. The assembly of this invention is designed tobe advanced through a portal formed in the patient. From the portal, theassembly is advanced through a potential space in the patient to thetarget location where the array is to be deployed. Tensions areselectively imposed on the steering cables to steer the sheath. Thissteering is necessary to direct the sheath, and the components encasedtherein, around obstructions so the sheath and encased components can bepushed to the target location. The sheath is considered at the targetlocation when the distal end of the sheath, the section holding thefolded electrode array, is disposed over the tissue against which thearray is to be deployed. Once the sheath is at the target location, thesheath is retracted away from the electrode array and the core. Theretraction of the sheath allows the release of the potential energy ofthe material forming the array frame. The release of this energy unfoldsthe array from around the core so the array is disposed against thetarget tissue. At this stage of the deployment process, the core remainsbetween the array and the tissue against which the array is to bedeployed. The core is retracted away of the unfolded electrode array.The array therefore seats against underlying tissue. Once the array isso seated, the array is considered completely deployed and ready foruse.

Applicant's PCT Pat. App. No. PCT No. PCT/US2010/029628 discloses how afolded over array can be steered to a location over the tissue againstwhich the array is to be deployed. However, this document does notteach: how the folded over array is initially percutaneously inserted inthe patient; how the array is initially positioned in the properorientation for advancement to the target location; or the structure oftool that can be used to both advance the sheath-encased array to thetarget location while steering the array. Also, the prior applicationdoes not disclose tools that can be used to first retract the sheathaway from the array and then retract the core from out from underneaththe folded over array.

SUMMARY OF THE INVENTION

This invention relates generally to system that: advances and positionsan implantable medical device over target tissue; deploys the positioneddevice; and retracts away from the device the components used tofacilitate the positioning of the array. The system of this inventionallows the device to be positioned and deployed percutaneously, that isthrough a relatively small portal, as opposed to a large incision,formed in the skin of the patient.

Medical devices that can be implanted using this invention includeelectrode arrays and stents.

The invention includes a core for supporting the device to be implantedand/or a sheath that surrounds the device. There is a handpiecedimensioned to be held in one hand. Integral with the handpiece is asteering unit. The steering unit controls one or more steering cablesthat extend to the device, the core or sheath. The steering unit iscontrolled by a manually actuated member attached to the handpiece. Thismanually actuated member is positioned to be controlled by thumb orfingers of the hand holding the handpiece.

Internal to the handpiece is a retraction assembly. The retractionsassembly is connected to the core supporting the device of the sheath inwhich the device is disposed. The retraction assembly retracts theattached core or sheath away from the device. The retraction assembly isactuated by a control member. This control member is mounted to thehandpiece to be actuated by the thumb or fingers of the hand holding thehandpiece.

If the implanted medical device is both supported by a core and encasedin a sheath, there are two retraction assemblies. A first retractionassembly retracts the sheath. A second retraction assembly retracts thecore. In some embodiments of the invention, a single control member isdepressed to actuate both retraction assemblies. In some embodiments ofthe invention, the retraction assemblies are arranged so that the firstretraction assembly at least partially retracts the sheath away from theimplanted device prior to the second retraction assembly withdrawing thecore away from the device.

The system of this invention also includes a guidewire and a dilatingintroducer sleeve.

The process of inserting and deploying an implantable device such as anelectrode array of this invention begins with the insertion of theguidewire into the patient. The guidewire is steerable. The guidewire isadvanced and steered toward the target tissue. Current may be sourcedfrom or sunk to electrodes on the guidewire. These current flows provideinformation regarding the location of the guidewire to the targettissue. The dilating introducer sleeve is threaded over the guidewire.The introduction of the sleeve expands the surrounding tissue so as toform a portal into the potential space into which the sheath is to beinserted. The sheath is then introduced into the patient through theportal.

Once the sheath is inserted, the sheath-encased electrode array isadvanced towards the target location. This is process is performed byadvancing the handpiece forward. Simultaneously with the handpieceadvancement, the steering assembly is selectively actuated. Theactuation of the steering assembly results in the off axis movement ofthe core and the components disposed over the core, the electrode arrayand the sheath. This off-axis movement of the core is what is employedto steer the electrode array to the target location. The steeringassembly is actuated by depressing a control member with a finger or thethumb of the hand holding the handpiece.

Once the electrode array is at the target location, the handpieceratchet is actuated. The ratchet is actuated using the fingers or thumbof the hand hold the handpiece. Initially, the ratchet retracts thedistal slide. This movement of the distal slide results in a likeretraction of the sheath away from the electrode array. As the sheathretracts away from the array, the potential energy stored in thematerial forming the array is released. The release of this potentialenergy unfolds the array. At this point in the deployment process, thecore remains disposed between the electrode array and the underlyingtarget tissue.

The practitioner continues to actuate the ratchet. This continuedactuation of the retractor results in the simultaneous retraction ofboth the distal slide and the proximal slide. The retraction of theproximal slide retracts the core out from underneath the electrodearray. Once the core is fully retracted, the electrodes of the electrodearray are disposed against the target tissue, the tissue through whichcurrent is to be flowed.

As a consequence of the complete retraction of the proximal slide, thepractitioner knows that the core is retracted away from the electrodearray. The practitioner then withdraws the handpiece, sheath and coreout of the patient to complete this portion of the insertion process.

The insertion assembly of this invention provides a means to identifythe target tissue prior to the insertion of the electrode array. Theassembly includes components useful for establishing a pilot path forthe electrode array to the target tissue. The handpiece of the assemblyis multifunctional. The handpiece allows a practitioner to perform thesteering needed to: position the electrode array at the target tissue;retract the sheath so that electrode array can unfold; and retract thecore so to cause the electrode array to seat over the target tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features and benefits of this invention are understood bythe following detailed description taken in conjunction with thefollowing drawings in which;

FIG. 1 is a perspective view of an insertion handle and the proximal endof a sheath of this invention;

FIG. 2 is a perspective view of an electrode array disposed around acore of the insertion handpiece;

FIG. 2A is an enlargement of a portion of FIG. 2;

FIG. 3 is a plan view of the handpiece of this invention, looking intothe base of the handpiece with the cover removed;

FIG. 4 is a plan view of one electrode array system of this inventionwith which this invention can be used;

FIG. 5 is a perspective view looking into the base of the handpiece;

FIG. 6 is a plan view looking into the base of the handpiece;

FIG. 7 is a cross sectional view of the handpiece base;

FIG. 8 a perspective view of the handpiece lid;

FIG. 9 is a top plan view of the handpiece lid;

FIG. 10 is a bottom plan view of the handpiece lid;

FIG. 11 is an exploded view of the distal slide and the componentsmounted to the distal slide;

FIG. 12 is a perspective view of the top of the distal slide;

FIG. 13 is a plan view of the top of the distal slide;

FIG. 14 is a perspective view of the underside of the distal slide;

FIG. 15 is a perspective view of the plate disposed over the distalslide;

FIG. 16 is a top plan view of the plate of FIG. 15;

FIG. 17 is a bottom plan view of the plate of FIG. 14;

FIG. 18 is an exploded view of the components forming the steering cabletensioner and tension limiter;

FIG. 19 is a cross sectional view of the sleeve of steering cabletensioner;

FIG. 20 is a perspective view of a steering block;

FIG. 21 is an end view of a steering block;

FIG. 22 is a perspective view of the steering button;

FIG. 23 is a perspective view of the underside of the steering button;

FIG. 24 is a perspective view of the proximal slide and the componentsattached to the slide;

FIG. 25 is perspective view of the proximal slide;

FIG. 26 is a perspective view of the underside of the proximal slide;

FIG. 27 is a perspective view of the cam lock;

FIG. 28 is an exploded view of the handpiece ratchet and the componentsattached to the ratchet;

FIG. 29 is a cross sectional view of the ratchet;

FIG. 30 is a perspective view of the pawl;

FIG. 31 is a perspective view of the ratchet release tab;

FIG. 32 is a partial perspective view of the core around which theelectrode is folded;

FIG. 33 is an enlargement of the view of FIG. 32 showing how the arraycable and system core extend forward from the sheath encased spring;

FIG. 34 is a perspective view of the core tip;

FIG. 35 is a cross sectional view through the sheath showing the coreforming wires and spring encased therein;

FIG. 36 is a cross sectional view through a distal portion of the sheathshowing how the electrode array is folded/bent around the core and thearray and core are both encased in the sheath;

FIG. 37 is a perspective view of the top of the strain relief;

FIG. 38 is a perspective view of the bottom of the strain relief;

FIG. 39 is a cross sectional view depicting how the strain relieve isconnected to the distal slide;

FIG. 40 is a perspective view of a stimulating guidewire of thisinvention when a straight stylet is disposed in the guidewire;

FIG. 41 is a cross sectional view of a stimulating guidewire when viewedalong a longitudinally extending plane;

FIG. 42 is a cross sectional view of a stimulating guidewire when viewedalong a plane that extends laterally through the guidewire;

FIG. 43 is a perspective view of the guidewire when a stylet with acurved distal end is disposed in the guidewire shell;

FIG. 44 is a perspective view of the introducer of this invention;

FIG. 45 is a cross sectional view of the introducer when viewed along alongitudinally extending plane;

FIG. 46 is a cross sectional view of the dilator hub when viewed along alongitudinally extending axis;

FIG. 47 is a cross sectional view of the introducer sleeve and dilatorwhen viewed along a plane that extends laterally across the introducer;

FIG. 48 is a cross sectional view of the introducer hub when viewedalong a longitudinally extending plane;

FIG. 49 is a cross sectional view illustrating how a portal is initiallyformed in tissue in order to insert and deploy an electrode arrayaccording to this invention;

FIG. 50 is a cross sectional view depicting the insertion of theguidewire of this invention;

FIG. 51 depicts the positioning of the of the inserter over theguidewire;

FIG. 51A is an enlarged portion of FIG. 51 depicting the distal end ofthe inserter over the guidewire;

FIG. 52 is a perspective view depicting the components contained in thesheath proximal to the folded over electrode array;

FIG. 53 depicts the insertion of the sheath encased electrode arrayaccording to this invention;

FIG. 54 depicts the partial retraction of the sheath away from theelectrode array and the partial deployment of the array;

FIG. 55 depicts the electrode array upon the full retraction of thesheath;

FIG. 56 depicts the partial retraction of the core from underneath theelectrode array; and

FIG. 57 depicts the deployment of the electrode array over the targettissue upon the complete retraction of the core.

DETAILED DESCRIPTION I. Overview

FIGS. 1 and 2 illustrate components of system 50 of this invention usedto percutaneously, insert, steer and deploy an implantable medicaldevice. This type of device provides a therapeutic benefit and/ordiagnostic information. The representative implantable medical device isan electrode array 30. System 50 includes a handpiece 52. Locateddistally forward of the handpiece 50 is a core 54. (Here “distal” meansaway from the practitioner holding the handpiece/towards the targetlocation. “Proximal” means towards the practitioner/away from the targetlocation.) The electrode array 30 is folded, or rolled, over the distalportion of the core 54. Proximal to where the electrode array 30 isfolded\bent\wrapped over the core 54, wires forming the core are securedover the outer surface of a spring 56 (identified in FIG. 33). The wiresforming core 54 and spring 56 extend proximally, into handpiece 52. Alsoextending forward from the handpiece 52 is a sheath 58. The sheath 58extends over the core 54. The sheath 58 also extends over the foldedover electrode array 30, core 54 and spring 56. (Only a portion ofsheath 58 is shown in FIG. 2 so that the system components disposed inthe sheath can be seen.) Two opposed steering cables 60 (FIG. 2A) aredisposed in the sheath 58.

As seen in FIG. 3, disposed inside the handpiece 52 are a distal slide62 and a proximal slide 64. Distal slide 62 is located forward of andinitially spaced away from proximal slide 64. Both slides 62 and 64 arecapable of moving longitudinally through handpiece 52. Sheath 58 isattached to the distal slide 62. Also attached to the distal slide 62are the steering cables 60. The steering cables 60 are connected to asteering unit 66 mounted to the distal slide 62. The core 54 formingwires and spring 56 are attached to the proximal slide 64.

Also mounted to handpiece 52 is a pivoting ratchet 68. Ratchet 68engages the distal slide 62. Actuation of ratchet 68 results in theproximally, rearwardly directed movement of both the distal slide 62 andthe attached sheath 58. Once the distal slide 62 moves rearward a setdistance, the continued movement of the distal slide 62 results in alike displacement of the proximal slide 64. Spring 56 moves with thedistal slide 64. Since the core-forming wire is attached to spring 56,this rearward movement of the proximal slide 64 results in a likemovement of core 54.

System 50 of this invention also includes a stimulating guidewire 510(FIG. 40) and an introducer 550. (FIG. 44). At the start of theprocedure for implanting the electrode array 30, guidewire 510 is usedto verify the location of the target tissue, alternatively, the “targetlocation,” over which the array is to be deployed. Introducer 550 isthen used to define the portal through which the sheath with encasedarray 30 is percutaneously inserted into the patient.

II. Electrode Array Assembly

FIG. 4 illustrates features of an electrode array 30 with which thesystem 50 of this invention is used. Array 30 includes a frame 32. Theframe 32 is formed from material that at a minimum is flexible, is ableto engage in some bending without undergoing plastic deformation. Frame32 is typically formed from material that is elastic, which is materialthat, upon removal of a deforming force, returns to its initial shape.More preferably, the frame 32 is formed from material that issuperelastic, material that when, subjected to an appreciable deformingforce or stress and then this force/stress is removed, returns to itsinitial shape. One such superelastic material is a nickel titanium alloyknown as Nitinol. Electrodes 34 are disposed on the frame 32. Theelectrodes 34 are the conductive components that abut the tissue againstwhich the array 30 is disposed.

The illustrated frame 32 has a tail 36 and head 44 spaced longitudinallyaway from the tail. Three parallel, laterally spaced apart bridges 38extend between tail 36 and the head 44. Each bridge 38 is formed to haveplural pairs of tabs 39. The tabs 39 comprising a pair of tabs extendoutwardly from the opposed sides of the bridge 38 with which the tabsare integral. Frame 32 is shaped so that each pair of tabs 39 thatextends outwardly from one bridge 38 is laterally aligned with a pair oftabs 39 that extend outwardly from the other bridges 38. The tabs 39that extend outwardly from adjacent bridges towards each other arespaced apart from each other. In the illustrated version of theinvention, since there are three bridges 38, in each row of tabs 39across the array 30, there are six tabs.

Frame 32 is further formed to have a number of beams 40. Each beam 40extends from one bridge 38 to the adjacent bridge 38. In the illustratedversion of the invention, beams 40 are arranged in longitudinallyaligned pairs. Each beam 40 that extends inwardly from one outer bridge38 to the center bridge 38 is aligned with a complementary beam thatextends inwardly from the outer bridge 38 to the center bridge 40. Alongthe length of the frame 32, the beams 40 are longitudinally spaced fromthe tabs 39.

The electrodes 34 are disposed on frame tabs 39. A number of arrays 30are constructed so that each electrode 34 is essentially disposed over aseparate one of the tabs 39.

Also part of the electrode array 30 are application specific integratedcircuits, ASICs, (not illustrated). These ASICs, which are not part ofthe present invention, contain current sources and current sinks. Thesecurrent sources and current sinks are connected to the electrodes 34.Some electrode arrays 30 with which the present system 30 is used areconstructed so that the ASICs are seated in openings formed in the frame32. Other electrode arrays 30 are designed so that ASICs are seated onthe surface of the frame 32. Conductors, again not illustrated and notpart of this invention, are disposed on the frame 32. The conductors arethe array components over which power and command signals are forwardedto the ASICs. The conductors serve as array components over whichsignals from the ASICs are transmitted off the array 30. Insulatinglayers, also not part of this invention and not illustrated,electrically insulate the components of array 30 and protect the arrayfrom the environment.

A cable 45 extends away from frame foot 36. Cable 46 contains wires (notillustrated) that are connected to the on-array conductors. The proximalend of cable 45 extends at least partially through the body of thepatient. Cable 45 is connected to an implantable device controller (IDC)46. The IDC 46 contains the power supply (battery pack) that powers theelectrode array 30. The IDC 46 also contains a processor that bothgenerates the instructions that regulate the operation of the electrodearray and that monitor the operation of the electrode array.

It should be understood that the structure of electrode array 30 and IDC46 is not part of the present invention. For example, the electrodearray may have conductors, vias, insulating layers and membranes thestructure of which, unless otherwise described, is not part of thepresent invention. This invention may be used with the electrode arraysthat are the subject of the Applicant's Assignee's PCT App. No.PCT/US/2010/044401 published as WO 2011/017426 and US Pat. Pub. No. US2012/0310316 A1 and PCT App. No. PCT/US2010/059691 filed 9 Dec. 2010,published as US 2012/0330393 A1, each of which is incorporated herein byreference.

III. Handpiece

Handpiece 52 includes a base 72 and cover 74 that collectively form thehousing or shell of the handpiece. Both the base 72 and cover 74 areformed plastic such as an ABS or polycarbonate plastic. Base 72, nowdescribed by reference to FIGS. 5-7, includes a bottom panel 78, twoside panels 80, a proximal panel 82 and a distal panel 84. Bottom panel78 is generally in the form of an elongated rectangle. In some versionsof the invention, bottom panel has a length between 15 and 30 cm. Instill other versions of the invention, bottom panel has a length between18 and 25 cm. A two section slot extends through the bottom panel 78.The slot includes a distal section 86. Distal section extends 86 extendsrearwardly from a position immediately proximal to the distal end ofpanel 78 a distance of around 55 to 65% of the length of the panel.Contiguous with and located proximal to slot distal section 86 isproximal section 88. The slot proximal section 88 is narrower in widththan slot distal section 86. Slot proximal section 88 extends rearwardfrom the proximal end of the distal section 86 a distance ofapproximately 10% of the overall length of the bottom panel. Both slotsections 86 and 88 are longitudinally aligned with and symmetric aroundthe longitudinal center axis of the bottom panel 78.

At the forward distal of the base 72, a reinforcing rib 90 extendsupwardly from the inner surface of bottom panel 78. The distal end ofslot distal section bisects rib 90. A bore 91 extends side to sideacross the base 72 through rib 90. The opposed ends of the bore 91 thusform openings in the opposed curved outer surfaces of the base that formthe transition sections between the bottom panel 78 and the side panels80.

The base 72 is further formed so as to define a notch 92. Notch 92 islocated in the portion of rib 90 located forward of the distal end ofslot distal section 86. Notch 92, like slot sections 86 and 88, iscentered on the longitudinal axis that extend along base bottom panel78. Base 72 is further formed so as to have two parallel ribs 94 thatextend upwardly from the inner face of surface of bottom panel 78. Ribs94 extend upwardly from the opposed longitudinally extending sections ofthe bottom panel 78 that define the opposed sides of slot distal section86. The ribs 94 extend distally from rib 90. Relative to the inner faceof the base bottom panel 78, ribs 94 are shorter in height than rib 90.The rails 94 extend proximally rearward of the proximal end of slotdistal section 86. Specifically, the ribs 94 extend to a longitudinalposition along the inner surface of the bottom panel approximately equalto where the proximal end of slot proximal section 88. The proximalsections of ribs 94 are spaced laterally away from the sides of slotproximal section 88. Ribs 94 provide structural strength to base 72.

Base bottom panel 78 is further shaped to have two longitudinally spacedapart divots 96 that extend inwardly from the inner surface of thepanel. Divots 96 are located proximal to the proximal end of slotproximal section 88. The divots 96 are centered on the longitudinal axisof the base panel 78. The openings defined by the divots 96 arerectangularly shaped. In cross section, in a plane that extendslongitudinally through the base panel 78, each divot has a semi-circularshape.

Side panels 80 extend upwardly from the opposed longitudinal sides ofbottom panel 78. Not identified are curved corners that form thetransition sections of the base 72 between the bottom pane 78 and theside panels 80. Each side panel 80 is formed so as to have a shoulder102 that extends outwardly from the outer surface of the panel. Eachshoulder 102 extends forward from the proximal end of the panel 80 withwhich the shoulder 102 is integral. Each shoulder 102 extends forward adistance approximately 15 to 25% of the length of the panel 80. Thedistal end of the shoulder 102 curves into the rest of remainder of theside panel 102. Each shoulder 102 is formed to have a threaded bore 103.The bore 103 extends inwardly from the exposed face of the shoulder 103,the face against which cover 72 abuts.

Within the base 72, each side panel 80 is shaped to have a step 104.Step 104 is defined by the curved, corner-defining section of the basethat is transition between the bottom panel 78 and the side panel 80with which the step is integral. Each step 104 thus extendsperpendicularly inwardly from the inner surface of the associated sidepanel 80. Steps 104 extend the length of side panels 80.

Two collinear ribs 106 and 108 extend inwardly from the inner surface ofeach side panel 80. Ribs 106 and 108 have an identical rectangular crosssectional shape. Rib 106, the proximal rib, extends distally forwardalong the associated side panel 80 from the adjacent inner face ofproximal panel 82. Each rib 106 extends forward to a position forward ofthe proximal end of the slot distal section 86. Ribs 108 are the distalribs. Each rib 108 is aligned with the associated proximal rib 106. Eachrib 108 extends forward from a position immediately proximal to theproximal end of base panel rib 90. Adjacent the inner faces of each sidepanel 80 where ribs 106 and 108 are present, the ribs extend over andare spaced above the underlying steps 104.

Proximal panel 82 extends upwardly from the proximal end of base panel78. The proximal panel 82 extends between the proximal ends of theshoulders 102 located at the ends of the side panels 80. Proximal panel82 is generally a planar structure. A tail 110 extends proximallyrearward from the exposed outer face of the proximal panel 82. Tail 110is generally oval shaped. The tail 110 is oriented so that the majoraxis of the tail is a vertical axis, an axis that that extendsperpendicularly upwardly from the plane 82 in which the base panel isseated.

The handpiece base 72 is further formed so that there are two bores intail 110. One bore, bore 112, is oriented along an axis that is parallelto the longitudinal axis of the base. Bore 112, extends both throughproximal panel 82 and tail 110. Bore 112 functions as an opening intobase 72. Owing to the shape of base 72, bore 72 is located above thecenter of tail 110. The second bore, bore 114 is a threaded bore(threading not identified). Bore 114 extends vertically, from the bottomof the tail into bore 112. A set screw 115, seen only in FIG. 5, isseated in bore 114.

Two stanchions 122 extend upwardly from the opposed corners of thedistal ends of the bottom panel rib 90. The outer side surface of eachstanchion 122 essentially forms the distal end of the associated sidepanel 80. The distal ends of ribs 108 abut the adjacent proximallydirected faces of stanchions 122. A threaded bore 124 extends inwardlyfrom the exposed face of each stanchion, the face directed towards theoverlying cover 74.

Base distal panel 84 extends forward from the upper portion of the basepanel rib 90 and sections of stanchions 122 located inwardly of the sidepanels 80. Distal panel 84 is thus located forward of the base panel 78and side panels 80. It should further be appreciated that the outerperimeter of the distal panel is located inwardly of the outer surfacesof the base panel 78 and side panels 80.

A nose 125 extends forward the outer surface of distal panel 84. Nose125 has generally an elliptical shape. Base 72 is formed so that majoraxis of the nose is in a plane parallel to and located above the planein which base panel 78 is seated. An elliptically shaped bore 126extends through both base panel 84 and nose 125. The longitudinal axisthrough bore 126 is coaxial with corresponding axis of bore 112.

Handpiece lid 74, now described with reference to FIGS. 8-10, includes atop panel 130. Top panel 130 has the same general length and width asbase bottom panel 78. A short distance proximal to the distal end of thetop panel 130, lid 74 is formed to have a circular through hole 132. Araised ring 134 extends upwardly from the outer surface of top panel130. Ring 130 defines hole 132. The height of ring 134 above top panel130 varies along the length of the panel. Specifically the most proximalportion of the ring extends above the top panel a relatively shortdistance forward of this portion of the ring 130, the height of the ringincreases incrementally. The most distal portion of ring 134 is thetallest portion of the ring. The ring 134 is formed so as to have athrough opening 133 in the most distal section of the ring. Opening 133extends radially through the ring 134 and downwardly towards the mostproximal portion of the ring,

Lid top panel 130 is further formed to have two parallel elongated slots135. Slots 135 extend forward from a location immediately distal to theproximal end of the panel 130. The slots 135 occupy a length thatextends approximately 20% of the total length of the top panel 130. Theslots are symmetrically spaced from and parallel to the longitudinalaxis of the lid 74.

A first reinforcing rib 136 extends above the outer surface of the toppanel 130. Rib 136 extends distally from ring 134. A second reinforcingrib 137, spaced proximally from rib 138 is also disposed over the outersurface of top panel 130. Rib 137 is located between slots 135. Rib 137extends distally forward from a location adjacent the proximal ends ofthe slots 136. Rib 137 extends forward of the slots 136. Rib 137 has anoverall length approximately two times the length of the slots. Ribs 136and 137 are axially aligned. A small bore 140 extends through rib 137and the underlying portion of top panel 130 immediately forward of theproximal end of the rib.

A closed end bore (not illustrated) also extends through most proximalportion of ring 134 into rib 136. This bore has the same diameter as andis coaxially aligned with ring opening 133.

Three collinear, longitudinally spaced apart ribs extend downwardly fromthe bottom surface of the lid top panel 130. The ribs are centered onthe longitudinal axis of the panel 130. A first one of the ribs, rib142, extends forward from the proximal end of the top panel 130. Rib 142extends downwardly from the portion of the top panel 130 located betweenslots 135. The width of the rib 142 is slightly less than that of thewidth of the section of the top panel 130 between the slots 135. Rib 142extends forward to a position proximal to the distal end of the slots135. Bore 140 extends through rib 137 into and through rib 142. The lid74 is shaped so that rib 142 has a distally directed face 144 with aconcave profile. Face 144 curves downwardly and proximally away from thesurface of the top panel 130 from which the face emerges. Face 144 has aradius of curvature of approximately 5 mm.

Spaced forward and away from rib 142, a second rib, rib 146, extendsdownwardly from the undersurface of the top panel. Rib 146 extendsforward to panel through hole 132. The rib 146 has a width less than thewidth of rib 142. Rib 146 is shaped to have at its proximal end adistally directed face 148. Rib face 148, like adjacent rib face 144,has a concave shaped profile. Thus, forward of where the rib face 144emerges from undersurface of the top panel 130, rib face 150 curvesdownwardly and proximally forward. The outer surface of the rib 146, thesurface that faces the base bottom panel 78, is formed with ridges 149.The ridges 149 extend across the rib 146 and, along the rib 146, arelongitudinally spaced apart from each other.

A rib 150 is the distalmost of the three collinear ribs 142, 146 and150. Rib 150 extends forward from through hole 132 to the distal end ofthe top panel 130. Ribs 146 and 150 are of the same width. Unlike withrib 146, the outer surface of rib 150 is smooth.

A rim 152 curves downwardly and outwardly from each side of the toppanel 130. Lid 74 is shaped so that the bottom surface of each rim 152will abut the adjacent top surface of each base side panel 80. Opposedtabs 154 extend outwardly from the proximal ends of the rims 152. Tabs154 are planar in shape. Lid 74 is shaped so that, when the lid isseated over base 72, each tab 154 seats over one of the base shoulders102. Each tab 154 is formed with a through bore 156. Bores 156 arepositioned so that when each tab 154 is seated over the complementarybase shoulder 102, the bore is in registration with an underlyingshoulder bore 103.

Lid 74 is further shaped so that forward of each tab 154, a bar 158extends downwardly from each rim 152. Each bar 158 is shaped so that,when the lid 74 is disposed over the base 72, the bar slip fits into thespace between the distal end of the adjacent base rib 106 and theproximal end of the adjacent base rib 108. The bars 158 are furtherdimensioned so that, when the handpiece 50 is assembled, the ends of thebars are located above the underlying steps 104 integral with base 72.

The lid 74 is further shaped to have a proximal panel 162. The proximalpanel 162 extends downwardly from the proximal end of the top panel 130and between the proximal ends of the rims 152. When the lid 74 isdisposed over the base 72, the lid proximal panel 162 abuts theunderlying base proximal panel 82.

The distal end of the lid top panel 130 is formed with a downwardcurving surface, (not identified). The top panel 130 is also formed tohave two through bores 162; one bore 162 in each distal end corner. Whenthe lid 74 is disposed over base 72, each lid bore 162 is inregistration over one of the base bores 124. In the illustrated versionof the invention, the lid top panel 130 is formed so that at each distalend corner there is a notch (not identified). Each bore 162 extendsthrough the lid 74 from the base of the associated notch.

A nose 164 extends forward from the most distal end of the lid top panel130. Nose 164 has a length, along the axis perpendicular to thelongitudinal axis of the lid 74, less than width across the top panel130. The nose 164 extends forward from the bottommost portion of thedistal end of the top panel. The top of the nose 164 is located belowthe outer surface of the top panel 130. The lid 74 is shaped so thatwhen the lid is seated over the base 72, lid nose 164 abuts base distalpanel 84.

The distal slide 62, and the components attached to the slide areinitially described by reference to FIG. 11. The slide 62 is a generallyrectangularly-shaped component dimensioned to seat on and slide overbase steps 104. The proximal end of the sheath 58 is secured to thedistal end of the slide. Steering cables 60 extend rearwardly out of thesheath and over the surface of the slide 62. The proximal end of eachsteering cable 60 is attached to tensioner 168. Each tensioner 168 ismounted to the slide 62. A plate 170 is disposed over the exposedsurface of the slide 62. Plate 170 holds the steering cables 60 andtensioners 168 to the distal slide 62.

Two steering blocks 172, part of steering unit 66, are moveably mountedto both the distal slide 62 and plate 170. Each steering cable 60 isthreaded through a separate one of the steering blocks 172.

The distal slide 62, now described by reference to FIGS. 12, 13 and 14,is formed from a plastic such as ABS. The distal slide is generallyrectangularly shaped. The slide 62 has a width that is approximately 1to 2 mm less than the distance between the base side panels 80. Thisallows the slide, when seated on base steps 104, to move longitudinallywithin the base 72. Extending forward of the main body of slide 62, theslide is shaped to have a nose 176. The nose 176 is formed to havewidth, a dimension perpendicular to the longitudinal axis of the base72, that is less than the width of the body of the slide 62. Distalslide 62 is further formed to have to have in its outer surface, aT-shaped indentation 178 that extends proximal rearward from the distalend of nose 176. The indentation 178 is T-shaped in that the portion ofthe indention that extends longitudinally across the nose 176 has anarrow width; the portion of the indentation that located in the mostdistal portion of the body of the slide 62 has a wider width.

The distal slide 62 is further formed to have a groove 180 that extendsproximally from indentation 178. Groove 180 extends the length of thebody of slide 62 and is centered on the longitudinal axis of the slide.The slide 62 is formed so that the groove 180 has a semi-circular crosssectional shape. Distal slide 62 is further formed to have two laterallyspaced apart blocks 182 that extend approximately 2 to 3 mm upwardlyfrom the top surface of the slide. Blocks 182 are located immediatelyproximal to the proximal end of indentation 178. The blocks 182 are onopposed sides of section of the slide 62 that defines groove 180. Blocks182 are formed so that three faces of each block, the distally directedface, the outwardly directed face and the proximally directed face, areplanner. The inwardly directed faces of the blocks 182, the faces of theblocks that are directed towards each other, are curved. Specifically,each face is curved so that, as the face extends proximally, away fromnose 176, the face curves outwardly, away from the longitudinal axis ofthe slide 62.

The distal slide 62 is also shaped to have two rectangularly shapedopenings 186. Each opening 186 is spaced proximally from one of theblocks 62. Each opening 186 essentially boarders the axial section ofthe base of the slide in which groove 180 is formed. Between theproximal end of a block 182 and the distal end of the aligned opening186, the slide is further formed to have a ramp surface 184. Extendingdistally from the block, the ramp surface 184 curves downwardly towardsthe underside of the slide. Ramp surfaces 184 have convex profiles. InFIG. 12 a set of wavy lines represent a slack section of a steeringcable 60 in one of the openings 186. This is to represent that, asdescribed below, when handpiece 52 is assembled, a section of eachsteering cable 60 extends into each opening 186.

Proximal to the proximal ends of openings 186, distal slide is formed tohave ramp surfaces 188. The distal end of each ramp surface 188 definesthe proximal end of each opening 186. Extending proximally, each rampsurface 188 curves upwardly. Ramp surfaces 188 have a convex shape. Thedistal slide has two pads 190. Each pad 190 is rectangularly shaped andextends approximately 2 to 3 mm above the outer surface of the slidebase. Pads 190 boarder the section of the slide 62 that defines thelaterally adjacent sections of groove 180. Each ramp surface 188essentially terminates at the proximal end of the adjacent pad 190.

The distal slide 62 is also formed with two pairs of channels. A firstpair of channels, channels 192, is located immediately proximal toindentation 178. Each channel 192 is located immediately inward of theinwardly directed face of an associated one of the blocks 182. Eachchannel 192 is located between the associated block 182 and the adjacentgroove 180—defining section of the slide. Channels 192 extend in rampsurfaces 184 and extend to the proximal ends of the ramp surfaces. Theportion of each channel 190 adjacent a block 182 curves with theadjacent block inwardly directed face. The portion of each channel 190formed in a ramp surface 184 extends linearly to the adjacent opening186. Owing to the curvature, it should be understood that the distal endof each channel is located closer to the longitudinal axis of the distalslide 62 than the channel proximal end.

The second pair of channels, channels 194, are formed in ramp surfaces188 and pads 190. Channels 194, like channels 192, are symmetricallylocated around the longitudinal axis of the slide 62. The portion ofeach channel 194 formed in the ramp surface 188 is linear and collinearwith the portion of channel 182 formed in ramp surface 184. The portionof channel 194 formed in the pad curves outwardly, away from groove 180.In the illustrated version of the invention, the proximal terminus ofeach channel 194 is located outwardly of the longitudinal center axis ofthe pad in which the pad 190 in which the channel is located.

Two symmetric grooves 198 are formed in the proximal section of thedistal slide 62. Grooves 198 are located adjacent to and on opposedsides of the section of the slide 62 in which groove 180 is formed.Grooves 198 are semicircular in shape and have a diameter greater thanthat of groove 180. Each groove 198 extends from a location adjacent theproximal end of the adjacent pad 190 to a location slightly distal tothe end of the base of the slide 62.

Molded into so as to be integral with the distal slide 62 are two caps196. Each cap 196 has a tube like body and, at its distal end, acircular top. Distal slide 62 is formed so that each cap 196 is moldedinto the distal end of one of a separate one of the grooves 198. Thedistal slide 62 is also formed so that a slot 197 extends longitudinallythrough each cap, including the distally directed head of the cap. Eachslot 197 terminates at the point where the associated channel 194 meetsthe cap 196 in which the slot is formed. The distal slide is furthershaped to have two U-shaped yokes 204. Each yoke 204 is located at theproximal end of one of the grooves 198. The yokes 204 extend above thesurfaces of the slide 62 that define grooves 198.

Extending proximally rearward from the proximal end of the slide body,distal slide 62 is formed to have a tail 206. The distal slide 62 isshaped so that the tail 206 is located below the upper surface of theslide body. Tail 206 is formed so that on the upper surface there aretwo longitudinally extending side surfaces 208 that are recessedinwardly relative to the center top surface (not identified), thesurface immediately below the proximal end of groove 180.

As seen in FIG. 14, distal slide 62 is formed to have an undersurfacethat is generally, though not completely, planar. The undersurfaces ofthe nose 176 and tail 206 are coplanar with the undersurface of thebody. A pair of arcuately shaped, parallel, bulges 210 extend downwardlyfrom the body undersurface. Bulges 210 are the portions of the body thatdefine grooves 198.

A rack 212 extends downwardly from the undersurface of the distal slide62. Rack 212 is located on the longitudinal axis of the slide 62. Therack 212 extends proximally from a location underneath blocks 172 underthe remainder of the body and along the whole of the tail 206. Rack 212is formed by a number of teeth 214. Each tooth 214 is in the shape of aright angle triangle wherein the distally directed surface extendsperpendicularly downwardly from the slide body and the hypotenusesurface extends upwardly and proximally away from the bottom end of thedistal surface (individual surfaces not identified).

The body of the distal slide 62 is further formed to have a number ofthreaded bores 216. In the illustrated version of the invention thereare eight threaded bores. One bore 216 is located adjacent each forwardcorner of nose 176. There is one bore 216 located outward of each block172. One bore 216 extends through each pad 190. Specifically, each ofthese bores 216 is located outward of the section of the channel 194formed in the pad 190. The remaining two bores 216 are locatedimmediately forward of the proximal end of the slide body. Each of thesebores 216 is located outwardly of an adjacent groove 196.

The plate 170 secured to the distal slide 62 is now described byreference to FIGS. 15-17. The plate 170 is formed from the same materialfrom which the distal slide 62 is formed. Plate 170 has a length equalto and width slightly less than the corresponding dimension of the bodyof the slide 62. The plate 170 has a generally planer body 218. Twopairs of posts 220 and 222 extend upwardly from the top surface of thebody. The two most distal posts, posts 220, are located immediatelyproximal to the distal end of the plate body 218. Each distal post 220is shaped so to have distally directed and outwardly directed faces thatare both planar and perpendicular relative to each other. Each distalpost also has a planar inwardly directed face that extends proximallyfrom the inner edge of the distally directed face. Between the opposedplanner inner and outwardly directed faces each post has an inwardlycurved face 221 that has a concave profile. Extending proximally fromthe contiguous inner directed planar face, this curved face 221 curvesoutwardly. Curved faces 221 of distal most posts 220 are directedtowards each other.

The two proximal posts, posts 222, are symmetrical and identical todistal posts 220. Each proximal post 222 has an inwardly curved face 223that is directed to both the curved face 221 of the adjacent distal post220 and the curved face 223 of the laterally adjacent proximal post 222.

Plate 170 is further formed to have two openings 226. Openings 226 arerectangularly shaped and have a common width equal to the width acrossthe distal slide openings 186. Each opening 226 has a length equal tothe combined length of an opening 186 and the adjacent ramp surfaces 184and 188. The plate 170 is formed so that, when the plate is disposedover the distal slide, each plate opening 226 is disposed over aseparate one of the slide openings 186.

A panel 228, part of plate 170, is located between openings 226. Theplate 170 is shaped so that panel 228 extends perpendicularly upwardlyfrom the outer surface of the plate. The panel 228 extends a shortdistance proximally beyond openings 226. A circular boss 230 extendsupwardly from the outer surface of plate 170 and is immediately proximalto the panel. A threaded bore 232 extends through the boss 230. Bore 232is concentric with the center longitudinal axis of the boss. 230. Aspring loaded ball 234, seen only in FIG. 16, is seated in bore 232.Ball 234 is positioned so as to extend above panel 228 and abut lid rib146.

Extending forward from the proximal end, plate 170 is formed to a have araised platform 242. Platform 242 has an outer surface that extendsupwardly from the outer surface of plate body 218. Not identified arethe curved sides of the platform 242 that form the transition betweenthe body 218 and the platform. Immediately forward of platform 242,plate 170 is formed to have two rectangular openings 236 in the platebody 218. Each opening 236 is shaped to receive one of the exposedsections of one of the caps 198 integral with distal slide 62. Alsointegral with the plate 170 is a spine 238 that is located over thelongitudinal axis of the plate. Spine 238 extends from boss 232, betweenopenings 236, to platform 242. The spine 238 has a rectangular crosssectional shape.

A number of bores 244 extend through the plate body 218. Plate 170 isformed to have six bores 244. Plate 170 is shaped so that when the plateis disposed over the distal slide 62, the plate bores 244 are alignedwith the six proximalmost bores 216 formed in the slide 62. In theillustrated version of the invention, the two most proximal bores 244are located in the plate body 218 forward of the proximal end of theplate. The two middle-located bores 244 are formed in the body on theopposed sides of boss 230. Each middle bore 244 is thus located betweenthe boss 230 and one of the proximally located posts 222. The distallylocated bores 244 are locate inwardly of the inner directed faces of thedistal posts 222. The distal bores 244 are centered on axes locatedforward of the distal end of panel 228.

The undersurface of plate body 218 is generally planar as seen in FIG.17. There are a number of upwardly extending indentations. One of theseindentations is a semicircular groove 248 that extends along thelongitudinal axis of the plate. Groove 248 has the same radius ofcurvature as slide groove 180. When the plate 170 is disposed over thedistal slide, the plate groove 248 is in registration over slide groove180.

The plate 170 is further formed so that extending proximally from thedistal end there are two notches 250. Notches 250 are symmetric aroundthe longitudinal axis of the plate 170. Each notch 250 is shaped toreceive one of the blocks 182 integral with the distal slide 62. Eachnotch 250 has a cross sectional profile, in a horizontal plane, thatallows a complementary distal slide block 182 to closely slip fit in thenotch. Consequently, each notch 250 is partially defined by a tab 251that extends upwardly from the base of the notch. Each tab 251 has alongitudinal surface that mirrors the adjacent curved surface of theassociated block 182. Each tab 251 is integral with an internal portionof the plate 170 that defines the adjacent groove 248. Notches 250 openinto plate openings 226.

Proximal to openings 226, the plate is formed to have two recesses 252the distal ends of which are contiguous with the openings 226. Recesses252 are located on the opposed sides of the sections of the plate thatdefines groove 248. Each recess 252 is shaped to have a rectangularshape. More particularly, plate 170 is shaped so that when the plate isseated over the distal slide 62 each slide pad 190 seats in one of therecesses 252. A bore 244 opens into each of the recesses 252.

Proximal to each opening 236, the underside of the plate platform 242 isshaped to define two semi-circular grooves 254. Grooves 254 have thesame radius of curvature as slide grooves 198. The grooves 254 extend tothe proximal end of the plate 170. When plate 170 is fitted over distalslide 62, plate groove 254 are disposed over slide grooves 198. Plate170 is further formed so as to have an arcuate rib 256 that extendsdownwardly from the inner surface of each groove 254-defining surface.Ribs 256 are located forward of the proximal ends of grooves 254. Whenhandpiece 52 is assembled, each rib 256 is in registration over acorresponding one of the slide yokes 204.

The structure of one of the steering cable tensioners 168 is a nowdescribed by reference to FIGS. 18 and 19. Each tensioner 168 includes asleeve 258, formed from a thermoplastic such as ABS. Each sleeve 258 hasa cylindrical body 259 with a distally directed head 260. A cylindricalclosed end bore 261 extends distally forward from the proximal end ofbody. Body 259 has an outer diameter less than that of the inner annularwall of the cap 198 in which the sleeve 258 is seated. The sleeve 258 isfurther formed so as to have an annular collar 262 that extends radiallyoutwardly around the body 259. Specifically, sleeve 258 is formed sothat the collar 262 is located forward of the proximal end of the body.Collar 262 has an outer diameter that allows it to slip fit between thecurved walls of the distal sleeve 62 and the plate 170 that,respectively, define a slide groove 198 and the complementary plategroove 254. The collar 262 is located on the sleeve 258 so that, whenthe sleeve is mounted to distal slide 62, the sleeve can movelongitudinally approximately 4 to 8 mm within the annular space formedby the complementary grooves 198 and 254.

Sleeve 258 is further formed to have a slot 263 the extendslongitudinally along the length of the sleeve. Slot 263 extends radiallyinwardly from the outer surface of the body 259 into bore 260. The slot263 also extends through collar 262. Slot 263 extends radially throughthe sleeve head 260 so as to terminate in the center of the head. Slot263 is dimensioned to facilitate the slip fitting of the steering cable60 into the bore 264.

The proximal end of each steering cable 60 is secured to cylindricalanchor 264 also part of the tensioner 168. In FIG. 18, the cable 60 isshown as a broken line. Often anchor 264 a thermoformed plastic such asABS and is molded over the proximal end of the steering cable 60. Anchor264 is dimensioned to slip fit within sleeve bore 261. The outer surfaceof anchor 264 is formed with threading (not identified). A nut 265 isthreaded over anchor 264.

Each tensioner 168 also includes a coil spring 270, seen only in FIG.18. Coil spring 270 is disposed around sleeve body 259. When thehandpiece 52 is assembled, each spring 270 extends between theproximally directed face of the slide cap 198 and the sleeve collar 262.Each spring 270 urges the associated sleeve 258 rearwardly. The rearwardmovement of the sleeve 258 is limited by the abutment of the sleevecollar 262 against the distally directed surfaces of the slide yoke 204and the plate rib 256. When the sleeve 258 so abuts the slide yoke 204and plate rib 256, the proximal end of the sleeve, the portion of thesleeve body 259 proximal to the collar 262 extends through and a shortdistance beyond the yoke 204 and rib 256.

When handpiece 52 is assembled, a steering cable 60, with anchor 264attached, is fitted in sleeve 258. Spring 270 is fitted over the sleeve258. The sleeve 258 is fitted in the appropriate slide groove 198. Theabutment of the sleeve collar 262 against the slide yoke 204 limits thespring-forced rearward movement of the sleeve 258 in the slide groove254. During the final assembly of the handpiece 54, nut 264 ispositioned on anchor 264 so that the nut bears against the proximallydirected face of sleeve 258. As discussed below, the nut 264 is set totake up slack and place a tension on the steering cable 60.

Steering blocks 172, one of which is seen best in FIGS. 20 and 21, arealso formed from the same type of plastic from which distal slide 62 isformed. Each steering block 172 includes a head 266. The head 266 isgenerally in the form of a rectangle with rounded corners. The head 266is dimensioned to fit with a slight clearance in the space definedbetween a pair of longitudinally aligned plate posts 220 and 222 and theplate panel 228. The outer corners of the head 266 are located inwardlyof the adjacent curved faces 221 and 223 of, respectively, posts, 220and 222. This dimensioning of the components of the handpiece 50 is tofacilitate the relative free movement of the steering block 172 betweenthe surrounding posts 220 and 222 and panel 228.

Each steering block head 266 is shaped to have an outwardly directedsurface that is not planar. More specifically, the top surface is shapedto so as to define along the length of the outer side a step 268 that isrecessed below the adjacent side surface, the surface proximal to thepanel 228. The step 268 extends the length of the head 266. The opposedundersurface of the head 266, the surface that is directed towards plate170, is planar (surface not identified).

A foot 272, also part of the steering block 172, extends downwardly fromthe head 266. Foot 272 extends downwardly from the inner side of thehead 266, the side adjacent plate panel 228. Each steering block foot272 has a cross sectional width that allows the foot to slide in one ofthe distal slide openings 186. Each foot 272 has a generallysemi-circular shape. The foot 272 extends downwardly from the inner sideof the shoulder, the side adjacent plate panel 228. Also, the foot 272is centered on the head 266 such that the ends of the foot are spacedinwardly from the distal and proximal ends of the head. Steering blockfoot 272 is generally semi-circular in shape with a base section 274adjacent the shoulder 228 that has a first radius of curvature. Belowthe base section 274 there is a head section 276 that forms the outermost end of the foot 272. Head section 276 has a second radius ofcurvature that is less than the first radius of curvature. Steeringblock foot 272 is further formed to have a groove 278 in its headsection 276. Foot 272 is formed so that groove 278 extends arcuatelyalong and in the outer arcuate face of head section 276. Groove 278 isdimensioned to receive one of the steering cables 60. The groove 278does not extend along the center axis of the face. Instead, the grooveis formed in the portion of the face adjacent the inner face of thehead, the face that is located closest to the plate plane 228.

Each steering block 172 is also formed to have L-shaped toe 280 thatextends radially outwardly from the portion of foot 276 most distal tohead section 266. Toe 280 extends outwardly from the outer portion ofthe arcuate face of the head section, the portion of the arcuate facethat is adjacent to and outward from the section in which the groove 278is formed. The outer end of the toe 280 is disposed over and spaced awayfrom the inner portion of the arcuate face of the head section, theportion of the head section in which groove 278 is formed.

When the handpiece 52 is assembled, each steering cable 60 is positionedover the distal slide 62 so that the cable is seated in the slide groove192, extends through the adjacent opening 186 and is seated in theassociated slide groove 194. As described above, the most proximal endof the cable is attached to the tensioner 168. Plate 170 is disposedover the body of the distal slide. Fasteners 245 extend through plateopenings 244 into slide openings 216 to hold the plate 170 to the slide62. Plate 170 thus holds the steering cables 60 and tensioners 168 tothe distal slide 172.

Each steering block 172 is fitted to the slide-and-plate assembly so theblock foot 272 is seated in one of plate openings 226 and underlyingslide opening 186. Each steering block foot 276 is thus located adjacentthe panel 228 that extends upwardly from plate 170. The section of thesteering cable 60 that extends through the slide opening 186 is threadedinto the groove 278 formed in the block foot 272. The steering cable isthus disposed between the block foot 272 and toe 280.

Handpiece steering unit 66 also includes a control button 282 that ispivotally attached to the lid 74. The button 282, now described byreference to FIGS. 22 and 23, is formed from the same material fromwhich lid 74 is formed. Generally, the control button 282 has a circularshape. More particularly, the diameter of the control button 282 isslightly less than that of lid hole 132. The relative dimensioning ofthe lid 74 and button 282 is to allow the button to freely pivot withinthe hole 132.

Button 282 is further shaped to have spine 284 that is generallycylindrically shaped. Spine 284 extends the longitudinal length of thebutton 282. The button 282 is further formed to have bore 286 thatextends axially through the spine 284. Two wings 288 that are symmetricwith each other around the spine 284 extend laterally away from theopposed sides of the spine. Immediately adjacent the spine 284 the wingthickness, the distance through the wing, is less than the distancethrough the spine. The button 282 is shaped so that, as the distancefrom the spine 284 increases, the wing thickness also increases. Thuseach wing 288 approximately has the shape of a pole-to-pole slicesection through a sphere.

A boss 290 extends downwardly from the underside of each wing 288. Thebosses 290 extend downwardly from the sections of the wings locatedlaterally to the spine. A line between the bosses 290 crosses the spineat 90°. Each boss 290 has an outermost face that is semi-spherical inshape.

A cylindrical pin 292, seen in FIG. 8, pivotally connects button 282 tohandpiece lid 74. Pin 292 extends through lid opening 133, button bore286 and lid bore 141. Owing to the relative dimensioning of the lid 74and the button 282, the button is able to, within lid through hole 132,pivot around pin 292.

The proximal slide 64, now described by reference to FIGS. 24-26, isformed from the same material from which distal slide 62 is formed.Proximal slide 64 is shaped to have a pair of laterally spaced feet 312.The slide 64 is shaped so that the lateral distance across the slide,the lateral distance between the outer edges of feet 312, isapproximately 0.25 to 0.5 mm less that the width across the opposedinwardly directed faces of the base side panels 80. Each foot 312 has awidth that is approximately 1 mm wider than the width across a base rib106.

Feet 312 are connected together by webs 314 and 316. Web 314, the distalof the two webs, extends proximal rearward from the distal ends of feet312. Slide 64 is shaped so that web 314 is slightly elevated relative tofeet 312. Web 314 is generally planar in shape. There are transitionsurfaces, not identified, along the sides of the web 314 where the webextends above the feet 312. The outwardly directed surface of the web314 is formed to have two parallel ribs 318 that extend the length ofthe web. Ribs 318 are symmetrically spaced apart from each other alongthe longitudinal center of the slide 64.

The more proximal of the two webs, web 316, is spaced longitudinallyfrom the proximal end of web 314. Web 316 extends forward from theproximal end of feet 312. The outwardly directed surface of web 316 iscoplanar with the outwardly directed surface of the feet 312. Web 316 isformed with a rib 320 that extends laterally across the slide 64. Rib320 is located between feet 312. A threaded bore 324 extends inwardlyfrom the outwardly directed surface of rib 320. A spring biased pindetent 326, seen only in FIG. 24, is fitted in bore 324. The pinintegral with detent 326 is dimensioned to seat in the bore 140 internalto lid rib 142.

The proximal slide 64 is further shaped to have a shoe 330 that extendsbelow the rib 320. The shoe 330 extends across rib 320; along an axisaligned with the longitudinal axis of slide 64. Shoe 330 has a generallytrapezoidal shape, the end of the shoe spaced distal to the rib 320 isshorter in length than the portion of the shoe adjacent the rib. Shoe330 is centered along the longitudinal axis of the slide 64. The slide64 is formed so that there is a through bore 332 in the shoe. Thethrough bore 332 is positioned so that, when the shoe is seated in base72, the bore 332 is coaxial with base bore 112. A toe 334 extendsforward from shoe 330. Toe 334 is an arcuately shaped member thatextends approximately 180° around and forward of the distally directedopening into bore 332. Toe 334, in addition to extending forward of shoe326 extends forward of rib 320.

A tube 335, seen only in FIG. 24, extends forward from proximal slideshoe 330. Tube 335 is formed from metal such as stainless steel. Theproximal end of tube 335 is adhesive or compression secured in shoe bore332. Tube 335 extends forward from the shoe 330 so as to extend belowand forward of slide distal web 314.

Proximal slide 64 has two pylons 336. Each pylon 336 is generally in theshape of a triangle. Each pylon 336 extends upwardly from a separate andoutwardly directed surface of a separate one of the slide feet 312.Below the apex of each pylon 336, each pylon is formed to have a bore338 that extends widthwise through the pylon. Bores 338 are thuscoaxial. It should further be understood that bores 338 are locatedalong an axis that is located over the void space in the slide 64between webs 314 and 316.

A cam latch 340, seen in FIGS. 24 and 27, is rotatably mounted betweenthe distal slide pylons 336. The cam latch 340 is formed from the samematerial from which the distal slide 64 is formed. Cam latch 340 has abeam 342 shaped to have a number of curved and straight surfaces.Specifically, beam 342 has a top surface 344 that is generally planar.Curved side surfaces 346 extend away from the opposed distally andproximally directed sides of the top surface 344. Overall, the top andside surfaces 344 and 346, respectively, of the beam are shaped so thatthe beam can seat in the void space between lid rib face 144 and lid ribface 148. Side surfaces 346 are convex curvature and are further shapedso as to be able to seat against rib faces 144 and 148. Opposite to andparallel with top surface 344, beam 342 is shaped to have a planarbottom surface 348. The beam bottom surface 348 has a width, the lengthacross the rib, the dimension parallel to the longitudinal axis of thedistal slide 64 that is greater than comparable width across the beamtop surface 344.

Cam latch 340 is further formed so that there is a tab 350 at each endof the latch. Tabs 350 are integral with beam 342. Each tab 350 is theform of a triangle that extends downwardly from an end of the beambottom surface 348. It should be appreciated that owing to the presenceof tabs 350, the length of the beam bottom surface 348, the dimensionperpendicular to the longitudinal axis of the slide 64 is less than thatof the length of the beam top surface 344.

A bore 352 extends side-to-side through the cam latch 340; through thebeam 342 and the opposed tabs 350. Bore 352 is centered on an axis thatis further from the beam top surface 344 than the bottom surface 348. Apin 354, the end of which is seen in FIG. 24, rotatably holds the camlatch 340 to the slide pylons 336. Pin 354 is seated in cam latch bore352. The opposed ends of the pin 354 extend out away from the opposedexposed faces of latch tabs 350. Each exposed end of pin 354 is seatedin one of the pylon bores 338.

A leaf spring 358, seen in FIG. 24 is mounted to distal web 314. Thespring 358 is formed from metal such as stainless spring steel. Spring358 is generally in the form of a U-shaped clip though the sections ofthe spring are of unequal length. The spring 358 is fitted around theslide web 314 so that the U-shaped bend projects rearward from thedistally facing front end of the web. The shorter of the two sections ofthe spring is disposed over the undersurface of the web 314. The longerof the two sections of the spring 358 extends over the top surface ofthe web 314 between ribs 318. The spring 358 is shaped so that theshorter of the two sections does not extend rearwardly beyond web 314.The longer of the two sections of spring 358 extends beyond the web to alocation rearward of where bores 338 extend through pylons 336. When theproximal slide is assembled, the longer of the two sections of spring358 bears against latch bottom surface 348. The abutment of the spring358 against the cam latch 340 inhibits rotation of the latch.

When handpiece 50 is assembled, the proximal slide 64 is mounted in thebase 72 so that the slide feet 312 rest on base ribs 106. The proximalslide 64 is positioned longitudinally in the base 72 so that when thelid 74 is in place, the cam latch 340 is disposed between lid ribs 142and 146. More particularly, the latch 340 is positioned so that one ofthe surfaces 346 is located adjacent face 144 of rib 142 and the opposedsurface 346 is adjacent face 148 of rib 146.

Ratchet 68, now described by reference to FIGS. 28 and 29, is formedfrom the same material from which the handpiece base 72 and lid 74 areformed. The ratchet 68 is an elongated member. The ratchet 68 has awidth that allows the ratchet to, with clearance, extend into slotdistal section 86 in the base bottom panel 78. The length of the ratchet68 is such that at least the top potion of the ratchet is able to seatin the slot distal section 86. Ratchet 68 is further formed so as tohave a top-to-bottom height that generally increases proximally from thedistal end of the ratchet. Not identified are the bumps on thedownwardly directed surface of the ratchet 68. These bumps function asfinger holds.

The ratchet 68 is further formed so as to have along the upwardlydirected face, the face directed towards handpiece base 72, a groove 380with a rectangular cross sectional profile. Groove 380 has a width widerthan the width across the rack 212 that extends along the underside ofthe distal slide 62. This dimensioning allows the rack to move withinthe groove. Groove 380 extends approximately along 60% of the length ofthe ratchet 68. A cavity 381 extends inwardly from the upwardly directedface of the ratchet 68. Cavity 381 is located proximal to the distal endof the ratchet and intersects groove 380. In cross section, along avertical plane through which the ratchet longitudinal axis extends,cavity 381 is seen to have a curved profile. More particularly, cavity381 is shaped to accommodate the feet 272 and toes 280 of steeringblocks 172. Proximal to groove 380, the ratchet 68 is formed to have avoid space 382. Void space 382 is contiguous with the proximal end ofgroove 380. Void space is both wider across than groove 380 and extendsdeeper into the ratchet 68 than groove 380.

Three bores extend laterally through ratchet 68. A first bore, bore 383,extends through the ratchet 68 immediately rearward of the distal end ofthe ratchet. The second bore, bore 384, extends through the ratchet soas to intersect the distal portion of void space 382. The third bore,bore 385, is located slightly rearwardly of and below bore 384. Bore385, like bore 384, extends through ratchet void space 382. The ratchet68 is further formed to have in an opening 386 that extends forward fromthe proximally directed face of the ratchet. Opening 386 opens into voidspace 382.

The distal end of the ratchet 68 is seated in the distal end ofhandpiece slot distal section 86. The distal end of ratchet 68 is thuslocated between the two sections of rib 90. A pin 388, seen in FIG. 28,extends through the bore 91 internal to the handpiece 54 and the coaxialratchet bore 383. Pin 388 pivotally holds the ratchet 68 to thehandpiece base 72.

A pawl 390, seen in FIGS. 28 and 30, is pivotally mounted to the ratchet68. The pawl 390 is generally in the shape of a bar. The pawl 390 has alength, width and height that allow the arm to seat entirely within theratchet void space 382. Pawl 390 is shaped to have a rearwardly directedface 392 that angles both downward and forwardly away from the adjacentupwardly directed face 394. Immediately proximal to the distal end ofthe pawl 390, a bore 395 extends laterally across the pawl. The pawl 390is further formed so as to have a groove 396 in the downwardly directedface of the arm, the face directed away from the handpiece base 72.

The pawl 390 is seated in ratchet void space 382. A pin 398 pivotallyholds the pawl 390 in the distal end of the ratchet void space 382. Pin398 extends through ratchet bore 385 and arm bore 395.

A torsion spring 402 normally urges the pawl 390 away from ratchet 68. Apin 404 holds the center coil section of the torsion spring 402 in theratchet void space 382. The opposed ends of pin 404 seat in ratchet bore385. Collectively, the spring 402 and pin 404 are located so that thecoil is located above the base of the void space slightly rearward ofthe interior surface of the ratchet 68 that defines the distal end ofthe void space. One arm of the spring 402 bears against the interiorwall of the ratchet 68 that defines the base of the void space 382. Theopposed arm of the spring 402 seats in pawl groove 396.

A release button 408, seen in FIG. 31, is slidably mounted in base slotproximal section 88. Button 408 has a plate 410. Extending forward andcoplanar with plate 410 is a head 412 and two arms 414. Head 412 isdimensioned to slidably fit in ratchet opening 386. Arms 414 are locatedon the opposed sides of head 412. Arms 414 are spaced apart a distanceslightly greater than the width across ratchet 68.

A fin 416 extends perpendicularly upward from plate 410. Fin 416 has awidth that allows the pin to slide in the base slot proximal section 88.A rectangularly shaped cap 418 is connected to and extends outwardlyaway from the top of fin 416. Cap 418 has a width across greater thanthe width across base slot proximal section 88. Button 408 is furtherformed so that the gap between plate 410 and cap 418 is slightly greaterthan the wall thickness of the handpiece bottom panel 78. A beam 420extends proximally from cap 418. A tab 422 extends downwardly from beam420, towards the underlying plate 410. Tab 422 is dimensioned to seat ineither of the divots 96 that extend inwardly from the inner surface ofthe base bottom panel 78.

When handpiece 50 is assembled, release button 408 is slidably mountedto the base bottom panel 78 so that the plate 410, head 412 and arms 414are located adjacent the panel outer surface, fin 416 extends throughslot proximal section 88 and cap 418 extends over the panel innersurface. Leg 420 and toe 422 extend over the inner surface of the basebottom panel 78.

IV. Core and Sheath

The system core 54, seen best in FIGS. 32 and 33, includes two parallelsections of wire 430. In one version of the invention, wire is formedfrom stainless steel and has a diameter of 0.2 mm. This wire, whileflexible, can withstand some axial loading. Wire 430 is bent so as tohave a U-shape and to define the two parallel sections of the wire.

The most distal section of the wire, the section of the wire thatincludes the actual U-shape bend, is encased in a plastic head 432. Head432, seen in FIG. 34, is formed from a plastic such as nylon. The head432 is formed to have a base 434. Base 434 has an oval cross sectionalshape. Forward of base 434, head 432 has a nose 436. Nose 436 has anoval cross sectional shape with a length and width greater than thelength and width of the base 434. The head is formed to have a U-shapedbore 438. The bore 438 has an opening on one side of the proximallydirected face of base 434 and extends into nose 436. Head 432 is furthershaped so that bore 438 curves around to have a second opening in theopposed side proximally directed face of base 434. Bore 438 isdimensioned to receive the core-forming wire 430. Head 432 may be moldedin place over wire 430. The molding of the head 432 over wire 430defines bore 438.

Core 54 further includes a pair of sleeves 440. Each sleeve 440 isdisposed over a section of wire 430 that extends proximally from head432. In one version of the invention, each sleeve 440 is formed from aflexible polymer such as LDPE and has an outer diameter of approximately1.5 mm. As seen in FIGS. 2 and 2A, wire 430 and sleeves 440 are shapedso that when the array 30 is wrapped around the core 54 each bridge 38is disposed over or under the longitudinal plane that extends betweenand parallel with sleeves 440. Each pair of electrode-supporting tabs 60at least partially subtends the sleeves 440. When the array 30 is sowrapped, the beams 40 conform around the outer surfaces of the sleeves440. Sleeves 440 are dimensioned such that, when the array beams 40 areso wrapped, the beams are not bent to the extent that the beams undergoplastic deformation.

The sleeves 440 extend proximally, rearwardly, along the sections ofwire 430 a distance approximately equal to the length of the array 30system 50 is intended to introduce and deploy. Core 54 can be consideredthe sleeve-encased sections of wire 430 and head 432.

Wire sections 430 extend rearward of core 54 and through the sheath 58as seen best in FIGS. 33 and 35. Rearward of the core 54, wires 430 aredisposed against spring 56. Spring 56 is a coil spring formed fromstainless steel. Given the helical shape of the spring 56, it should beappreciated that a lumen, not identified, extends axially through thespring. The spring 56 is further formed so that the diameter of thisspring lumen is slightly greater than the outer diameter of the cable 45that extends proximally from the array 30. In one version of theinvention, the diameter of the spring lumen is approximately 1 to 2 mmgreater than the diameter of the array cable 45.

The opposed sections of wire 430 are disposed against diametricallyopposed portions of the outer surface of spring 56. In the illustratedversion of the invention, the spacing between the core 54—forming wiresections are spaced slightly closer apart from each other than moreproximal portions of the section of wire 430 that are disposed againstspring 56. Accordingly, immediately distal to the front end of thespring 56, each section of wire 430 includes a bend 446. Each bend 446is the transition of the portion of the wire section that form the core54 and the portion of the wire section that abuts spring 56.

A flexible tube 448 is disposed over spring 56 and the overlying wires430. Tube 448 is a formed from a heat shrinkable material such as PTFE.The tube 448 when heat shrunk, has a wall thickness of approximately0.05 mm. As a consequence of the heat shrinking of tube 448 over thesections of wire 430 and the spring 56, the wire sections are heldagainst the spring 56 by the tube.

The spring 46-wire 430-tube 448 assembly extends proximally through thehousing nose bore 126. This assembly seats in bore collectively formedby distal slide groove 180 and plate groove 248. The proximal end ofthis the wire 430-spring 56-tube 448 assembly is disposed in the tube335 integral with proximal slide 64. More particularly, the wire430-spring 394-tube 448 assembly is solder secured in the open enddistal end of tube 335.

Disposed inside of, and extending rearwardly with, spring 56 is thearray cable 45. In FIG. 35 a biocompatible polymer sleeve 459 is shownas being disposed around the array cable 45. Sleeve 459 is also shown ashaving an inner diameter greater than the outer diameter of the cable45. In practice, the sleeve 459 may be integral with and tightlysurround the wires internal to cable 45. It should be understood thatthe cable 45, including the surrounding insulating sleeve, aredimensioned relative to the lumen defined by spring 58 so that the cable45 and spring 56 are able to move freely relative to each other.

Sheath 58 of system 50 of this invention is formed from a biocompatiblepolymer such as nylon. As seen best in FIGS. 33 and 35, sheath 58 has agenerally oval cross sectional shape. More particularly, the sheath isshaped to have parallel top and bottom panels 460 and 462, respectively.Panels 460 and 462 each have a thickness of approximately 0.75 to 1.25mm. Side panels 464 extend between the top and bottom panels 460 and462, respectively. Each side panel 464 curves outwardly relative to theedges of the adjacent top and bottom panels 460 and 462. Collectively,panels 460, 462 and 464 define a lumen 466 that extends axially throughthe sheath. Sheath 58 is further formed so that each side panel 464 hasan inwardly extending rib 468. Each rib 468 projects inwardly from theside panel 464 with which the rib is associated so that ribs aredirected toward each other. A bore 470 extends through each rib 466.Bores 470 thus extend longitudinally through the opposed sides of sheath58. In FIG. 35, sections of the steering cable 60 are shown in the bores470.

Sheath 58 is shaped so that the minor axis in lumen 466, the distancebetween the adjacent inner faces of top panel 460 and bottom panel 462is slightly greater than the width across the array 30 when folded overthe core 54. In some versions of the invention, this lumen width isapproximately 0.5 mm greater than the distance between the outer surfaceof bridge 38 and the outer surface of the outer of the two folded underbridges 38. This lumen width is such that, when the array is disposed inthe sheath 314, the lumen prevents the energy stored within the foldedsuperelastic beams of the carrier from unfolding the array 40. In FIG.36, for ease of illustration, gaps are shown between the outer surfaceof the folded over bridges 38 and the adjacent inner surface of sheathtop and bottom panels 460 and 462, respectively. In reality, the carrieris unfolded to the maximum extent allowed by the sheath 314. Sheath 314is outwardly stretched as a consequence of this unfolding of thecarrier. The sheath 314, as seen in FIG. 36, stretches outwardly toaccommodate spring, wire and tube assembly. System 50 is constructed sothat sheath 58 extends proximally rearward from the head 432 from whichwires 430 extend.

Each steering cable 60 is disposed in a separate one of the sheath bores470. Each cable 60 is formed from stainless steel and has a diameter ofapproximately 0.15 mm. Cables 60 extend out from the proximal end ofsheath 314 and are connected to the steering assembly. Each steeringcable 60 extends through the associated bore 470 to the distal end ofthe bore.

An anchor 472 holds the distal end of each steering cable 60 in thedistal end of the associated sheath bore 470. In one version of theinvention, the anchor 472 comprises a strand of wire wrapped around thedistal end of the cable 60. This wire may be a preformed coil spring.Solder secures the spring to the steering cable 60. Each anchor 472, asdepicted in FIG. 36 has an outer diameter larger than that of thesteering cable 60. In FIG. 36 for ease of illustration the anchors 472are seen simply as large diameter sleeves disposed over the ends of thecables 60 with which the anchors are integral. The outer diameter ofeach anchor 472 is, relative to the sheath bore 470 is sufficientlylarge so that the portion of the sleeve that defines the bore holds theanchor in place. In some versions of the invention, an adhesive, such asepoxy, is further used to hold each anchor 472 in the distal end of theassociated sheath bore 470.

A sleeve 476 extends longitudinally over each cable 60. Sleeves 476 areformed from stainless steel or other material that is less flexible thanthe encased steering cables 60. Collectively, sheath 58, cables 60 andsleeves 476 are constructed so that the sleeve-encased cables 60 canseat in sheath bores 470. While not apparent in the drawings, in manyversions of the invention, the components forming system 50 areconstructed so that there is clearance between the outer surface of eachsteering cable 60 and the adjacent inner wall of the surrounding sleeve476. This clearance may be 0.05 mm. This clearance facilitates themovement of the cable 60 in the sleeve. There may also a clearancebetween the outer surface of the sleeve 476 and the adjacent internalwall of the sheath 58 that defines the bore 470 in which the sleeve isseated. This clearance facilitates the seating of the sleeve 476 in thebore. In some versions of the invention, the outer diameter of eachsleeve 476 is 0.05 mm smaller relative to the sheath bore 470 in whichthe sleeve 476 and associated cable 60 is seated.

The distal end of each sleeve 476 is located approximately 1 cm rearwardof the distal end of the adjacent tube-encased spring 56. The proximalends of the sleeves 476 are essentially adjacent the proximal end of thesheath 56 in which the sleeves are encased.

Sheath 58, including the components encased therein, extend proximallythrough the handpiece nose bore 126. A strain relief 478 is overmoldedover the proximalmost 8 to 15 cm of the sheath 58, the portion of thesheath that extends through the housing nose bore 60. The strain relief478 is formed from a thermoplastic such as nylon. Strain relief 478, nowdescribed by reference to FIGS. 37 and 38, has a tube like stem 480.Stem 480 is the portion of the strain relief 478 overmolded over theproximal end section of sheath 58. The stem 480 is shaped to define anumber of notches 482 that extend inwardly from its outer surface. Thenotches 482 are in planes that are perpendicular to the longitudinalaxis of the stem 480. The notches 482 reduce the stiffness, increase theflexibility, of the stem 480. In the illustrated version of theinvention, the strain relief is formed so that the most proximal portionof the stem, a portion having a length of approximately 1 cm, is notchfree. Stem 480 is further formed so that the proximal section can seatin indentation 178 formed in the distal slide 62.

Also part of the strain relief 478, two ears 484 are formed integrallywith stem 480. Ears 484 extend laterally outwardly from the top portionof the proximal end of the step. Here, the stem “top portion” isunderstood to be the portion of the stem directed away from the proximalslide 62. The strain relief 478 is formed so that that the opposed innerand outer surfaces of ears 484 are generally planar and parallel. Eachear 484 is formed with an oval shaped opening 486. The strain relief 478is formed so that the major axes of openings 486 are collinear. A collar488, also part of strain relief 478, extends between over the proximalend of stem 480 so as to extend between ears 484. The bottom and sidesurfaces of collar 488 are rectangular in shape.

Strain relief stem 480, like the enclosed proximal end portion of thesheath 58, extends through housing nose bore 126. The strain relief ears484 are disposed over the distal slide 62 so that the proximal end ofthe stem 480 and collar 488 are disposed in slide indentation 178. Moreparticularly, the components of system 50 are constructed so that strainrelief collar 488 is closely slip-fitted into the wide width proximalportion of indentation 178 as seen in FIG. 39. Strain relief ears 484are positioned over the slide so that each opening 486 its disposed headopenings 488 are in registration with the distalmost slide bores 216.Threaded fasteners 490 that extend through the strain relief openings488 into the slide bores 216 hold the strain relief to the distal slide.Since sheath 58 is integral with the strain relief 478, fasteners 490,by extension hold the sheath 58 to the slide.

When handpiece 50 is assembled, spring 56 and steering cables 60 extendproximally rearward out of sheath 58 and strain relief 478. As discussedabove, tube 335 holds spring 56 to proximal slide 64. Steering cables 60also extend out of the proximal end of the sheath. As discussed above,each steering cable 60 passes through the grooves formed on the distalslide 62, is threaded through one of the steering blocks 172 and is tiedto one of the tensioners 168.

V. Stimulating Guidewire and Introducer Sleeve

System 30 of this invention also includes a stimulating guidewire 510(FIG. 40) and an introducer 550 (FIG. 44). At the start of the arrayimplantation procedure, guidewire 510 is used to generally identify thetarget tissue over which the implantable medical device, array 30,should be deployed. Once this location is identified, introducer 550 isslip fitted at least partially over the guidewire 510. Introducer 550 isthen advanced a short distance into the potential space into which thesheath encased electrode array is subsequently introduced. Guidewire 510is then retracted out of the introducer 550. A lumen through introducer550 functions as the guide path through which the sheath-encasedelectrode array 30 is percutaneously inserted into the patient.

The guidewire 510, now described by reference to FIGS. 40-42, includes ashell 514 formed from a flexible biocompatible thermoplastic. Shell 514is generally in the form of an elongated tube. In many versions of theinvention, the shell has a maximum outer diameter of 3.0 mm. Thisfacilitates the insertion of the shell in the lumen of a needle. Theshell 514 is, however, further formed so as to have a closed distal end.The shell 514 is shaped to have a nose 516, which is the most distalportion of the guidewire and a trunk 518 that extends proximally fromthe nose. Shell trunk 518 has a diameter greater than that of shell nose516. In one version of the invention, the shell nose 516 has an outerdiameter of approximately 1.0 mm; shell trunk 518 has a diameter ofapproximately 1.5 mm. Not identified is the tapered transition sectionof the shell 514 between nose 516 and trunk 518. The shell 514 has acentral bore 520 as well as a number of auxiliary bores 522. Bores 520and 522 are closed end bores. Central bore 520 extends axially throughthe shell 514 and terminates at a location proximal to the distal end ofthe shell nose. Auxiliary bores 522 are equiangularly spaced apart fromeach other relative to the central longitudinal axis of the shell 514.The centers of bores 522 are equidistance from the center of bore 522.Also, while not illustrated in the drawings, the guidewire may be formedso that the auxiliary bores 522 extend helically through the shell 514.Guidewire 510 is formed so that the auxiliary bores 522 terminate at thedistal end of the shell trunk 518. In the version of the version of theinvention wherein the shell trunk 518 has an outer diameter ofapproximately 1.5 mm, central bore 520 has a diameter of approximately0.4 mm; the auxiliary bores 522 have a diameter of 0.25 mm.

Four tube-like sleeves 524 formed from electrically conductive materialare disposed over the shell trunk 518 so as to be, along the length ofthe guidewire 510, longitudinally spaced apart. Some versions of theguidewire 510 are constructed so that the inner diameters of the sleeves524 have an inner diameter that is less than the outer diameter of theshell trunk 518. In versions of the invention wherein the outer diameterof the shell trunk 518 is approximately 1.5 mm, each sleeve 524 may havean inner diameter of approximately 1.25 mm and a wall thickness of 0.25mm. Each sleeve 524 functions as an electrode through which current canbe sourced to or sunk from the tissue against which the guidewire 510 isdisposed.

Current is sourced to or sunk from each guidewire sleeve 524 by aspecific conductor 526 that extends through the shell trunk 518. In theillustrated version of the invention there are four sleeves 524.Therefore, there are four conductors 526. Each conductor 526 is disposedin a separate one of the shell auxiliary bores 522.

Guidewire 510 is further constructed so that a number of sections ofheat shrink tubing 530 are disposed over the shell trunk 518. The tubingforming the heat shrink tubing is selected so that, as a result of thetube sections 530 compressing around the shell trunk 518 the trunksections over which the tube sections 530 are disposed have a greaterouter diameter than the trunk sections over which the conductive sleeves524 are disposed.

In some methods of manufacturing the guidewire 510 of system 50 of thisinvention, slits or other openings (not illustrated) are formed in theshell trunk 518. Each slit/opening extends into a separate one of theshell auxiliary bores 522. More specifically, each slit/opening isformed in a section of the shell trunk 522 over which a sleeve 524 is tobe located. Once the slits/openings are formed, the sleeves 524 aredisposed over shell trunk 518. Owing to the relative dimensions of theshell trunk 518 and the sleeves 524, and the flexible nature of thematerial forming the shell 514, the sleeves and conductors 526essentially press through the slits/openings to abut. Thisshell-to-conductor contact establishes the electrical connection betweenthese two components. In some versions of the invention, theshell-to-conductor contact can be further established by welding or asolder joint. In some method of manufacture, the welding causeslocalized ruptures in the shell trunk through which theconductor-to-sleeve connections are formed. This eliminates the need toform slits in shell trunk 522.

In one method of manufacturing guidewire 510, a rigid rod is initiallyinserted in the shell center bore 520 to provide the shell with somerigidity. Conductors 526 are then threaded into the shell 514. Thenecessary slits are cut in the shell trunk 518. Sleeves 524 are then fitover the shell trunk. Once the sleeves are in place, a piece of unshrunkheat shrink tubing is fitted over the shell trunk. The tubing is thenshrunk. The shrunk tube extends over the edges of sleeves 524 to holdthe sleeves in place.

The proximal ends of the conductors 526 extend out of the proximal endof the guidewire shell 514. Conductors 526 are connected to an externaltest module. This test module contains current sources, current sinksand components for measuring the voltages present at the sleeves 524.The structure of this test module and connections to it (both notillustrated) is not part of the present invention.

When the guidewire is prepared for use, a flexible stylet 532 isdisposed in the shell central bore 520. The stylet 532, while havingsome degree of flexibility, is less flexible than the shell 514. In someversions of the invention, the stylet 532 is formed from Teflon coatedstainless steel. If the central bore 520 has a diameter of approximately0.4 mm the stylet has a diameter of approximately 0.3 mm. Stylet 532 isfitted in the shell 514 so as to extend into the portion of the centralbore 520 formed in the nose 516.

The stylet 532 disposed in the shell 514 may be straight. With a stylet532 so shaped, the guidewire 510 itself generally has a straight shape.Again it should be appreciated that, while the guidewire 510 is straightit is also flexible. Alternatively, the stylet 532 disposed in theguidewire shell 514 may have a distal end tip that is bent or curvednear the nose. (Stylet not illustrated.) When this particular type ofstylet 532 is fitted in the shell 514, the guidewire itself, as seen inFIG. 43, develops a curve along its longitudinal axis. It may bedesirable to flex the guidewire 510 into the curved state when there areobstructions between where the guidewire is inserted into the patientand the location against where it is believed the electrode array 30should be deployed. In these situations, curving the guidewire nose canmake it easier to steer the guidewire around the obstructions.

The introducer 550 is now described by initial reference to FIGS. 44 and45. At the most proximal end, the introducer 550 includes a dilator hub552. A sleeve hub 570 is removably attached to and extends forward fromthe dilator hub 552. A tube like sleeve 590 is attached to and extendsforward from the sleeve hub 570. A flexible dilator 596 is attached toand extends forward from the dilator hub 552. The dilator 596 extendsthrough both the sleeve hub 570, the sleeve 590 and out forward from thedistal end of the sleeve.

The dilator hub 552, seen in FIGS. 44 and 46, is formed a single pieceof thermoplastic such as a polycarbonate plastic. At the most proximalend, the dilator hub 552 has a base 553 that is generally oval shaped. Apedestal 554 extends distally forward from the base 553. In crosssection, in a plane perpendicular to the longitudinal axis of theintroducer 550, the pedestal 554 appears to have a shape of a rectanglewith rounded corners. The dilator hub 552 is further shaped so that asthe pedestal 554 extends distally forward the sides of the pedestaltaper inward. In the illustrated version of the invention, dilator hub552 is shaped so that the most distal portion of the pedestal 554 isstepped inwardly from the base 553. Immediately forward of the pedestal554, the dilator hub 552 is shaped to have a head 556 that forms themost distal portion of the hub 552. Head 556 is in the shape ofrectangular block with rounded corners.

As seen in FIG. 46, dilator hub 552 is further formed so as to have fourconcentric bores 558, 560, 562 and 564 that collectively form a throughpath that extends through the longitudinal center axis of the hub. Bore558, the most proximal of the bores extends forward from the proximallydirected face of hub base 553. Bore 558 extends through the base 553 andsubstantially through the pedestal 554. Bore 560 extends forward fromthe distal end of bore 558. Bore 560 has a diameter less than that ofbore 558. The diameter of bore 560 is, however, slightly greater thanthat of the guidewire shell trunk 518. Bore 562 extends forward of bore560. Bore 562 has a diameter approximately equal to that of bore 558.Bore 564, which extends forward of bore 562, opens in the front end ofthe dilator hub 552. Bore 564 has a diameter greater than that of bore562. A groove 565, shown only in cross section in FIG. 46, extendspartially around hub head 556. Groove 565 is in a plane perpendicular tothe longitudinal axis through dilator hub head 556. Groove 565 is onlyin a portion of one face of head 556.

The dilator 596 is an elongated flexible member formed from a plasticsuch as LDPE. As best seen in the cross sectional view of FIG. 47, incross section, the dilator generally is oval shaped. The cross-sectionwidth and height of body of the dilator, the portion of the dilatordisposed in sleeve 590, approximate the corresponding dimensions ofsheath 58 when the array 30 is encased in the sheath. Forward of thebody of the dilator, the dilator is formed to have a tip 598. Extendingdistally from the main body of the dilator 596, the cross sectionalwidth and height of tip 598 decreases. Dilator 596 is further formed soas to have bore 602 that extends axially through the dilator along thewhole of the length of the dilator. Bore 602 is dimensioned to receivethe guidewire shell trunk 518. A marker 604, such as a material opaqueto X-rays, may be disposed around the dilator tip 598.

The most proximal end of dilator 596 is mounted in dilator hub bore 560.An adhesive may be used to hold the dilator 588 to the hub 552.

The sleeve hub 570, now described by reference to FIGS. 44 and 48, isformed from the same material from which dilator hub 552 is formed. Thesleeve hub 570 has a body with a cross sectional shape of a rectanglewith rounded corners. The cross sectional width and height of the sleevehub 570 are equal to the corresponding width and height of the proximaladjacent dilator hub head 556.

Two contiguous bores 574 and 576 form a longitudinal through paththrough the sleeve hub 570. Both bores 574 and 576 are centered on thelongitudinal axis of the hub 570 and are oval in cross sectional shape.More particularly, both bores 574 and 576 are dimensioned to receive thedilator 596. A first one of the bores, bore 574, extends distallyforward from the proximal end of the hub body 574. The second bore, bore576, extends forward from bore 574. Bore 576, unlike bore 574 is furtherdimensioned to receive sleeve 590. Not identified is the step betweenbores 574 and 576 that forms the base of bore 576. Bore 576 is oval inshape and is centered on longitudinal axis of the hub body 570. Whilethe major and minor axes through bore 576 are slightly greater than,respectively the cross sectional height and width of the body of dilator588. A notch 578 extends inwardly from one side of hub body 570. Thenotch 578 extends into and is contiguous with bore 574. The distal endof notch 578 is spaced slightly proximally from the step between bores574 and 576. Notch 578 is formed to have an undercut, (not identified)that extends proximally such that the undercut is located within theshell body 572. This undercut is contiguous with the proximal portion ofbore 574. A number of closed end bores 577 extend rearward inward fromthe proximally directed face of sleeve hub body 572. Bores 577 arepresent for manufacturing reasons only.

Sleeve hub 570 is further formed to have a foot 578 that extendsproximally rearward from the proximal face of the hub. Foot 578 islocated inwardly from the outer perimeter of the hub 570. The sleeve hub570 is shaped so that, when the hub 570 abuts the dilator hub 552, foot578 extends into the open end of the dilator hub bore 564. The seatingof foot 578 in bore 564 inhibits the relative rotation of the dilatorand sleeve hubs 552 and 570, respectively. The sleeve hub 570 is furtherformed to have a groove 580, shown only in cross section in FIG. 48.When dilator hub 552 and sleeve hub 570 are fitted together, dilator hubbore groove 565 and sleeve hub groove 580 are located on the same sideof the introducer 550.

A steering tab 581 is moveably mounted to the sleeve hub 570. Steeringtab 581 is seated in hub notch 576. The steering tab 581 has a fingerlike bar 582 that is disposed in the undercut of notch 576. A tab 582extends outwardly from bar 581 out of hub notch 576. The tab has a base,not identified, that rests on the inner wall of hub body 572 that definethe distal end of notch 576.

A lock plate 583 is removably mounted to both dilator hub 552 and sleevehub 570. In one version of the invention, the lock plate 583 is providedwith pins (not identified). One lock plate pin seats in dilator hubgroove 565, the second pin seats in sleeve hub groove 580.

Sleeve 590, like dilator 596 is oval in cross sectional shape. Thesleeve is formed from stainless steel braid reinforced polyether blockamide such one sold under the trademark Pebax by Arkema of Colombes,France and has a wall thickness of approximately 0.25 mm. Notillustrated are the braids internal to sleeve 590. Wires 591 extendlongitudinally through the sleeve 590. The lumen that extends throughthe sleeve (lumen not identified) is dimensioned to slidably receive thesheath encased electrode array 30. The proximal end of the sleeve 586 isadhesively secured to the inner wall of the sleeve hub 570 that definesbore 576. The distal end of the sleeve 590 abuts the step between bores574 and 576. In the illustrated version of the invention, a reinforcingcollar 593 is seated in hub bore 576. Collar 593 extends over theproximal section of sleeve 590 adjacent sleeve hub 570. When theintroducer 550 is assembled, sleeve 590 extends over dilator 590. Thesleeve 590 does not extend over the whole of the dilator 590. The sleeve590 is dimensioned so that the sleeve distal end is located slightlyproximal to where the dilator tip 598 tapers inwardly from the rest ofthe dilator body. The most distal end section of sleeve 590 has a taper,illustrated but not identified in FIG. 44, that extends over theunderlying tapered portion of the dilator tip 598.

One or two of the wire strands 591 are connected steering tab 581(connection not shown). The displacement of the steering tab 581 resultsin the like displacement of the attached wire strands 591. Thedisplacement of the wire strands 591 results in the flexure of thesleeve 590.

VI. Operation

One step in implanting an electrical array 30 using system 50 of thisinvention is the initial determination of the general location of thetarget tissue over which the array is to be deployed. This step isperformed using diagnostic techniques and equipment that are not part ofthis invention.

After the general location of the target tissue is identified, a portalis formed in the body adjacent the target tissue. FIG. 49 illustrateshow a portal 698 is formed when the array 30 is to be deployed over thespinal cord 702. When the array 30 is employed to flow current throughthe neurological tissue forming the spinal cord, the array is disposedover the dura 704 in the epidural space 706. The dura 704 is theprotective tissue that surrounds the CSF, the arachnoid, thesubarachnoid space and the nerves forming the spinal cord. The epiduralspace is the potential space within the spinal column between the dura704 and the ligamentum flavum, the tissue that connects the individualvertebrae together that forms the spine. This process starts with theinsertion of an epidural needle 710 between two vertebrae. A stylet 712is typically seated in the needle 710 during this process. The punctureformed by the epidural needle 710 defines the portal 698 in the patientthrough which the other components of system 50 are inserted into thepatient. It will be noted from the Figures that the distal end of theepidural needle is curved. The opening out of the needle is on the sideof the needle 710. During this process, the epidural needle 710 isinserted into the patient so that the open end of the needle is directedtowards the target tissue.

Once the portal is initially formed, stylet 712 is removed from theneedle. (step not illustrated).

The guidewire 510 is then fed through the cannula of needle 710 as seenin FIG. 50. Owing to the curvature at the distal end of the needle 710it is observed that as the guidewire 510 exits the needle, the guidewirecurves away from the dura 704. As the guidewire 510 continues to bedischarged from the epidural needle 710, the guidewire travels over thedura 704. A fluoroscope may be used to track the position of theguidewire 510.

During the procedure, straight and curved stylets may be sequentiallyfitted in the guidewire 510. This facilitates the steering of theguidewire towards the vicinity region in which it is believed theimplantable medical device, array 30, should be deployed.

When the guidewire conductive sleeves 524 are in the vicinity of thetarget tissue, the advancement of the guidewire is terminated. Theguidewire conductors 526 are connected to the external test module. Thisstep may be performed before the guidewire 510 is inserted in theepidural space. Currents are sourced from/sunk to the sleeves 524 tocause flows through various sections of the target tissue. The responseof the patient to these current flows is monitored. This testing isperformed to determine if the current flow through the target tissueshows some indications of the intended beneficial effects of the flowthe array 30 will provide and/or does not cause intolerable sideeffects.

As a result of this process there may be some readjustment of theposition of the guidewire 510 to find the location where the currentflow results in the optimal combination of beneficial therapy andtolerable side effects. A fluoroscope or other device may be used tomark the location over the spinal cord 702 over which the guidewiresleeves 524 (electrodes) are positioned when this further defined targettissue is identified.

The epidural needle 710 is then removed from the patient. (Step notillustrated). To perform this sub-procedure, it is often necessary tofirst disconnect the test module from the guidewire conductors 524. Atthe conclusion of this process, the guidewire 510 remains in thepatient. More specifically, the proximal end of the guidewire 510extends out of the portal 698.

Introducer 550 is then inserted in the patient. In this process, dilator596 is slid over the guidewire 510. The dilator 596 is threaded over theguidewire 510 so that the guidewire extends through dilator bore 602.The guidewire 510 extends proximally out of dilator hub bore 558. Thepractitioner then grasps and pushes forward on hubs 552 and 570 toadvance the sleeve 590 and the dilator 596 through the portal 60subcutaneous tissue as seen in FIG. 51. (In FIG. 51 and FIG. 53 for easeof illustration the proximal end of the hubs of the introducer 550 arenot shown.) The cross sectional area of the dilator 596 is greater thanthe guidewire 510. Accordingly as the sleeve 590 and dilator 596 advancethrough the tissue, the dilator 596 expands the size the portal into thepatient. In the presently described procedure, the sleeve and dilatorare feed over the guidewire to at least the point where the guidewirecurves and starts to extend linearly over the dura 704.

Sleeve 590 and dilator 596 tend to be less flexible than guidewire 510.This stiffness of the sleeve 590 and dilator 596 are what enable thesleeve and dilator to expand the muscle, the inter vertebral ligamentsand the ligamentum flavum through which they are inserted. Thisstiffness reduces the ability of the sleeve 590 and dilator 596 to turnwhen emerging from between the vertebral bodies into the epidural space.Accordingly, in the portion of the process in which the sleeve 590 anddilator 596 are so advanced, tab 581 is manipulated to place a tensionof sleeve strand 591. This tension flexes the sleeve 590 and encaseddilator 596. The flexing of the sleeve 590 and dilator 596 causes them,when further advanced to advance the guidewire 510, to turn towards thetarget tissue, as seen in FIGS. 51 and 51A.

Once the sleeve 590 and dilator 596 are positioned, the guidewire 510and dilator 596 are withdrawn (steps not illustrated). Initially, theguidewire 510 is pulled out of the dilator bore 602 and the dilator andsleeve hubs 552 and 570, respectively. Dilator 596 is then withdrawnfrom sleeve 590. This process starts with uncoupling of the lock plate582. At a minimum, the lock plate 582 is decoupled from at least one ofthe dilator hub 552 or the sleeve hub 570. In some procedures, the lockplate 582 is decoupled from both hubs 552 and 570. The practitioner thenpulls proximally on the dilator hub 552 so as to extract the dilator 596from sleeve 590. In some procedures, the practitioner holds sleeve hub570 to prevent proximal displacement of the sleeve 590. At this time,the sleeve 590 remains in the portal and is ready to accept thesheath-encased electrode array 30.

The actual insertion of the array 30 into the patient begins with thethreading of the sheath encased array into first the sleeve hub 570 andthen sleeve 590. For ease of illustration, the sleeve 590 is shown inFIG. 53 having a greater thickness than as depicted in FIG. 51. At thistime, as seen in FIG. 52, it should be appreciated that extendingproximal back into the handpiece 52 are: cable 45 containing the wiresthat extend to the array 30; spring 56; steering cables 60; and theproximal portions of core forming wires 430. Spring 56, it will berecalled, is attached to tube 335 integral with the proximal slide 64.The array cable 45 extends out the distal end of the tube 335 and out ofthe proximal end of handpiece 54 through tail bore 110. Often, prior tothe insertion of the sheath encased array 30 in the portal 698, setscrew 115 is set to clamp the section of cable 45 disposed in handpiecetail 110.

Once the proximal end of the sheath 58, the end in which the array 30 isdisposed, is disposed in the sleeve 590, the practitioner with one hand,holds handpiece 52 and, with the other hand, the section of the sheath56 immediately adjacent the introducer sleeve hub 570. The pushingforward of the handpiece 52 results in a like forward displacement ofthe array 30 and sheath 58. Spring 56 resists some axial loading.Accordingly, the spring 56 as well as the electrode array 30 disposed infront of the spring are axially advanced with the sheath 58.

As a result of the prior removal of dilator 596 from sleeve 590, some ofthe tissue surrounding the sleeve may have compressed the sleeveinwardly. The braids internal to sleeve 590 resist at least some of thecompression of the sleeve. Accordingly, the lumen internal to sleeve 590has a cross sectional area that if not equal to that of sheath 58 is notappreciably smaller than that of the sheath. Further the tissuesurrounding the sleeve 590, having previously expanded away once fromthe portal, has a compliancy that was not previously present. Thiscompliancy reduces the force needed to, when threading sheath 58 throughthe sleeve 590, expand the tissue outwardly in order to advance thesheath. Thus, during the initial part of the array insertion process,large amounts of manual force are not required in order to introduce thearray 30 into the patient.

During this process of advancing array 30 towards the target tissue,handpiece ratchet 68 is seated in handpiece slot section 86. Releasebutton 408 is set so the button head 412 seats in ratchet opening 386.The engagement of the release button 408 with the ratchet 68 holds theratchet in the retracted state in which it is partially disposed withinthe handpiece 52. Also at this time, the distal slide 62 is in itsforwardmost position. Release button toe 422 is seated in distalmosthandpiece notch 96. Owing to the positioning of the distal slide 62,each steering block 172 is disposed under a separate one of the steeringbutton bosses 290. More particularly, each steering button boss 290 isdisposed immediately above a separate one of the steering boss steps268. The slide spring loaded ball 234 is seated between two of theridges 149 in lip rib 146. This engagement of the ball 234 with ribs 146holds the distal slide 62 in its distalmost position. Cam lock 340 isdisposed between lid ribs 142 and 146. The cam lock 340 thus holds theproximal slide in a fixed position forward of handpiece proximal panel82.

As the sheath encased electrode array exits the sleeve 590, the arraymoves along the dura 704. During this and other movement of the array,the array may encounter tissue that resists this motion. Spring 56prevents the axial buckling of the array and sheath 58 that can occur inresponse to this resistance. The position of the sheath 58, moreparticularly the distal end in which the array 30 is encased, may betracked with a fluoroscope.

As the sheath 58 is advanced to over the target tissue, it may benecessary to steer the sheath. The practitioner performs this act bypressing downwardly on the appropriate one of the wings 288 of button282. The practitioner performs this action with the thumb or finger ofthe hand holding handpiece 52. This displacement of the button 282results in the boss 290 integral with the depressed wing 288 pressingagainst the step 268 of the adjacent steering block 172. The steeringblock 172 is therefore displaced downwardly relative to the distal slide62. The downward displacement of the steering block 172 results in alike displacement of the section of the steering cable 60 threaded tothe block. It will be recalled that, owing to the adjustment of nut 265,the steering cable 60 already is in tension. Consequently, thedisplacement of steering cable 60 by the steering block causes thedistal end of the cable to move towards the handpiece 52. It is recalledthat the distal end of the steering cable 60 is anchored in the distalend of the sheath bore 470 in which the cable is seated. The retractionof the distal end of the steering cable 60 causes the side of sheath 58through which the cable extends to flex towards the handpiece 52. Thesleeve 476 through which the cable 60 extends limits the extent to whichthe retracting cable is able to flex the sheath. Specifically, thesheath flexure primarily occurs where the sleeve 476 is not present; thedistal end of the sheath 58, the section of the sheath in which thearray 30 is encased. This flexure of the sheath thus allows the sheathto, as it is advanced towards the target position, be steered aroundobstructions that inhibit linear advancement of the sheath.

As a consequence of the depression of steering button 282, steeringcable 60 may be subjected to a significant amount of force. This canoccur for example, if the tissue adjacent the distal end of the sleeve58 opposes the flexure, the turning, of the sleeve. If the cable issubjected to more than a specific amount of force, the force on thecable will be greater than the force spring 270 imposes on sleeve 258.Should this event occur, instead of the cable 60 continuing to pull itsdistal end rearwardly, the cable, through anchor 264 and nut 265, pullsthe tensioner 258 distally, towards the front end of handpiece 52. Thisfeature of the invention reduces the likelihood that so much force willbe placed on the steering cable distal to the handpiece that the cablewill either separate or damage other components of the insertion system50 of this invention. In some versions of the invention, each tensionerassembly 168 is designed so that the spring 270 will begin to compresswhen the cable 60 through connected components places 5 pounds (22.25Newtons) force on the spring.

Eventually, the distal end of the sheath 58 is disposed over the targettissue, the tissue against which the electrode array 30 is to bedeployed. Once the practitioner is in this stage of the procedure, it isnecessary to both deploy the electrode array 30 and retract the core 54and sheath 58 away from the array and out of the patient. This processbegins by the release of ratchet 68 from the retracted state. This stepis performed by the manual displacement of release button 408proximally. Specifically, button 408 is retracted so that button toe 422seats in the more proximal two of the notches 96 internal to thehandpiece base 72. The retraction of button 408 allows the release ofthe potential energy stored in spring 402. The spring 402 pushes pawl390 upwardly so as to result in the opposed downward pivoting movementof ratchet 68.

The practitioner then, with the fingers of the hand holding handpiece52, repeatedly pulls upwardly on the ratchet 68. This manual forceovercomes the force spring 408 outputs in holding the ratchet 68 in theextended state. This displacement of ratchet 68 causes the free end ofthe pawl 390, the end associated with face 392, to engage against one ofthe teeth of distal slide rack 212. The motion of the pawl 390 againstthe rack 212 pushes the distal slide 62 rearwardly, towards handpieceproximal panel 82. This manual force the practitioner exerts againstthrough the ratchet 68 and pawl 390 on the distal slide 62 is enough toovercome the force of the spring that holds ball detent 234 against thehandpiece rib 146. Therefore the distal slide 62 is displacedrearwardly, towards the handpiece proximal panel 82. The proximalmovement of the distal slide 62 results in a like movement of theattached sheath 56.

During this initial rearward displacement of the distal slide 62, thedistal slide 62 is spaced from the proximal slide 64. As the distalslide 62 continues to move rearward, the distal slide 62 moves under theproximal slide 64 so as to not have any contact with the slide or anycomponents attached to the slide 64. Consequently, the rearward movementof the distal slide 62 has no effect on the proximal slide 64.

During this stage of the sheath and core retraction sub-steps, cam latch340 is seated between lid rib faces 144 and 148. Leaf spring 358prevents rotation of the cam latch 340 away from ribs 142 and 146.Spring 358 prevents the movement of the cam latch 340 and the cam latchprevents movement of the proximal slide 64. Core 54 is connected to theproximal slide 64. Given that, during this phase of the sleeveretraction step, the proximal slide 64 is in a static position withinthe handpiece 52, a fixed length section of core 54 remains extended outfrom the handpiece 52.

After each phase of a ratchet pivoting cycle in which the ratchet 68 ismanually displaced towards the handpiece 52, the practitioner releasesthe grasp on the ratchet. Spring 402 returns the ratchet 68 to theextended state.

As a result of this rearward displacement of the sheath 58, the sheathmoves proximally away from the distal end of the core 54, the end overwhich the electrode array 30 is folded. The movement of the sheath 58away from the folded over array 30 allows the potential energy stored inthe folded over/bent away frame 32 to be released. This energyunfolds/unbends the array 30 so that the sections of the array foldedover/under the core 54 unfold/unbend away from the core as seen in FIG.54. When the electrode array 30 is so unfolded/unbent, the array isconsidered in the deployed state. When the array 30 is in the deployedstate, the electrodes 34 face the target tissue, the tissue throughwhich current is to be flowed.

As seen by FIG. 55, immediately after the full retraction of sheath 58away from the electrode array, the core 54 remains disposed between thearray and the target tissue. Core 54 is retracted away from the array 30by the continued pivoting of ratchet 68. As a consequence of theresultant further displacement of the distal slide 62, the proximalfacing edge of plate 170 abuts cam latch tabs 350. Since spring 358inhibits the rotation of the cam latch 340, tabs 350 likewise resistdisplacement. This resistive force the spring 358 places on the camlatch 340 causes the latch to initially resist the further rearwarddisplacement of the distal slide 62. The tactile feedback thepractitioner feels in overcoming this resistance provides an indicationthat any additional pivoting of ratchet 68 will result in the retractionof core 54.

To actually retract the core 54, the practitioner initially applies aslightly stronger manual force of the ratchet 68 to cause the continueddisplacement of the distal slide 62 than was required to simply retractthe sheath 58. As a result of this displacement of the distal slide, theproximal end of the attached plate 170 is moved against the cam latchtabs 350 with sufficient force to overcome the force spring 358 placeson the cam latch 340 to hold the latch in position. The cam latch tabs350 are rotated upwardly. More particularly, each tab rotates into oneof the slots 135 formed in handpiece lid 74. This causes a correspondingdownward rotation of the cam beam 342 away from the space between lidribs 142 and 146. As a result of this displacement of cam latch 340,distal slide 62 is able to move underneath proximal slide 64.

As a result of the movement of the distal slide 62 underneath theproximal slide 64, the proximal end of the distal top panel 170 abutsproximal slide shoe 330. When the ratchet 68 is actuated to force thedistal slide 62 further rearwardly, distal slide 62 now pushes proximalslide 64 in the same direction. The proximal slide 64 moves overhandpiece ribs 106. The wire sections 430 forming core 54 are attachedto the proximal slide 64. This during the simultaneous rearwarddisplacement of slides 62 and 64 in handpiece 52, both the core 54 andthe sheath 58 are retracted rearwardly away from the proximal end of thedeployed electrode array 30. As seen in FIG. 56, the core 54 isretracted away from its position between the electrode array 30 and thetarget tissue. In FIG. 56, a section of the center-located frame bridge38 is removed to show the presence of the core head 432 below thedeployed electrode array 30.

During the process of retracting the proximal slide 64 it should beunderstood that both spring 58 and tube 335 are simultaneouslyretracted. The electrode array cable 45 extends through both spring 56and tube 335. The clamping of the cable 45 by set screw 115 in thehandpiece tail 110 inhibits the rearward movement of the cable. Theblocking of cable 45 from rearward movement inhibits similar rearwardmovement of the array 30 away from over the target tissue. Since cable45 is disposed within spring 56, the spring prevents the cable frombuckling.

Slides 62 and 64 are simultaneously retracted towards the handpieceproximal panel 78. Eventually the proximal slide pin detent 360 movesinto registration with bore 140 internal to handpiece lid 74. The pinintegral with detent 360 moves into lid bore 145. The seating of the pinin bore 140 blocks further movement of the proximal slide 64 and, byextension distal slide 62. The perception of the absence of thisresistance when the ratchet is further pressed to retract the slides 62and 64 functions as tactile feedback to the practitioner that the core54 and sheath 58 have been retracted as far away as possible from theelectrode array 30 with the handpiece. FIG. 57 represents the array 30disposed over the target tissue, dura 704, once the core is fullyretracted away from the array.

The process of retracting the core 54 and sheath 58 completely out ofthe patient then proceeds with the loosening of screw 115 in thehandpiece tail 110. This allows the handpiece 52 and attached componentsto be passed over cable 45. The handpiece is then so moved away from thepatient while the cable is held stationary relative to the targettissue. This retraction of the handpiece away from the patient resultsin a like withdrawal of the core 54 and sheath 58 from out of portal698.

Once the handpiece 52, core 54 and sheath 58 are completely removed fromthe patient, sleeve 590 is removed from the patient by the practitionerpulling the sleeve hub 570 away from the patient. It should beappreciated that in this process, the sleeve hub 570 and sleeve 590 arepassed over the whole of the portion of cable 45 that extends out of thepatient.

Once hub 570 and sleeve 586 are removed, cable 45 is trimmed to length.Cable 45 is then tunnel connected to the IDC 46. This assumes the IDC 46is already implanted in the patient. Current can then be flowed throughthe electrodes in order to obtain the desired therapeutic effect

System 50 of this invention thus functions as an assembly useful forinitially providing an indication if the current flowed through thetarget tissue will offer a benefit to the patient and/or ensuring thatthe side effects are tolerable. The system 50 then provides a means todefine an initial portal 698 into the patient that is directed towardsthe target tissue. Once the system provides the portal, the handpiece 52of system 50 is used to both advance the electrode array 30 towards thetarget tissue and steer the array towards the tissue. Handpiece 52 isdesigned so that the practitioner can with a single hand both hold thehandpiece to advance the electrode array, and with the thumb or a fingerof that hand depress button 282 that steers the array. Once theelectrode array is over the target tissue, again using the hand holdinghandpiece 52, the practitioner depresses ratchet 68. The depression ofthe ratchet 68 results first in the retraction of the sheath 58 fromaround the array 30 and then the retraction of the core 54 fromunderneath the array.

Thus, system 50 of this invention provides a convenient means for bothaccurately percutaneously positioning an electrode array 30 over targettissue and, once the array is so positioned, deploying the array. Aspart of the deployment process, the components of the system used toposition the array are retracted out of the patient without appreciablydisturbing the deployed array.

VII. Alternative Embodiments

The above is directed to one specific version of this invention as wellas one specific method of use. Alternative versions of this inventionmay have alternative structures and uses in alternative surgicalprocedures.

For example, there is no requirement that all versions of this inventionbe used with the described electrode array 30. Other versions of thisinvention may be used with electrode arrays that have features differentfrom what has been described. Thus, it may be desirable to use thisinvention in order to position an electrode array that, once positionedover the target tissue does not unfold or unbend. In these versions ofthe invention, the electrode array may simply rest on the core. Theinvention may be used to insert and deploy medical devices that offertherapeutic benefits or diagnostic information other than electrodearrays and stents.

Likewise, there is no requirement that all versions of the inventioninclude both a core and a sheath for positioning the electrode arrayover the target tissue. In some versions of the invention, it may not benecessary to provide a core for supporting the electrode array. In theseversions of the invention the electrode array is simply encapsulatedinside the sheath. Using a modified handpiece of this invention, thesheath and electrode are steered to the target tissue. Once theelectrode is over the target tissue, the single slide internal to thehandpiece, the slide to which the sheath is attached, is retracted. Thisretraction of the sheath exposes the electrode array to the targettissue.

Still other versions of the invention may not include a sheath that isdisposed over the implantable medical device. In these versions of theinvention, the core functions as a support that is advanced in order toseat the overlying implantable device over the target tissue.

Alternatively, in some versions of this embodiment of the invention, thewires forming the core may be the wires that are steered. In theseversions of the invention, a portion of the core proximal to the arraymay be encased in a sleeve or sleeves that inhibit flexure of thecore-forming wires. In this version of the invention, when a steeringtension is imposed of one of the core wires, only the distal end of thewire is flexed, steered.

Likewise there is no requirement that all versions of this inventioninclude an assembly for steering the electrode array.

In some versions of the invention, the core 54 that serves as thecarrier for the electrode array 30 may not be separate from the systemcomponents proximal to the core that advance the core to over the targettissue and then retract the core. For example, in some versions of theinvention, the wire forming the core may be a distal end extension ofthe wire forming the spring that extends proximally from the core.Alternatively, instead of being formed from metal, the electrodecarrying core and structure extending distally therefrom may be formedfrom other materials. Thus, in some versions of the invention, the coremay be formed from a section of plastic. The system component thatextends distally from the core may be plastic tube constructed to beboth flexible and resist axial buckling. These two components may beformed from a common piece section of plastic or formed from twodifferent pieces of plastic that are bonded together. Similarly, one ofthese components can be plastic and the other metal.

The steering unit may likewise take other forms. For example, it may bedesirable to provide a steering unit either attached to the sheath orthe core that has three or more steering cables. At least one ofsteering cable is not linearly aligned with at least two of the cables.This version of the invention would thus allow the core to be steerednot just left or right but also up or down. Similarly, the steeringunits that selectively tension or slack the steering cables may bedifferent from what has been described. In some versions of theinvention, the steering assembly may be a rotating pair of opposed arms.Each steering cable, assuming two such cables is attached to the freeend of a separate one of the arms. The rotating of the armstensions/slacks the steering cable. A knob mounted to handpiece 52 isrotated to cause a like rotation of the arms. Alternatively, thesteering cables may be mounted to slides. Buttons mounted to thehandpiece to slide along the handpiece are displaced to tension andslack the steering cables.

If components of the steering unit are attached to the slide, in someversions of the invention, these components may be attached to the slidethat retracts the core 54. Some steering units of this invention may nothave components attached to either slide.

The retraction units that retract the core 54 and sheath 58 need notalways each be slides. For example, one or more of these retractionunits may be spindles. This type of The core or sheath is attached tothe spindle. The actuator, when activated, rotates the spindle. Therotation of the spindle results in the attached core or sheath wrappingaround the spindle.

An actuator other than the disclosed ratchet system may be employed toretract the core 54 and/or sheath 58. Thus one retraction system maysimply be some sort of finger hold that extends from the slide, throughthe handpiece. The practitioner grasps and retracts the finger hold todisplace the slide to which the finger hold is attached.

Versions of the invention with two retraction units may have two controlmembers, one for each retraction unit. This arrangement allows thepractitioner to independently control the actuation of each retractionunit. This would allow the practitioner to independently control theextent to which the core and sleeve are retracted away from the medicaldevice being implanted. If this construction of the invention, bothcontrol members would be acceptable by a thumb or finger of the handholding handpiece 52. One construction of this version of the invention,the control members are triggers. Each trigger is repetitively pulled tocause the retraction of the associated core 54 or sheath 58.Alternatively, independently displaced slide buttons function as thecontrol members for the individual retraction units.

Depending on the device the handpiece 50 is employed to implant, theretraction units may be configured so that, when first actuated, bothunits are simultaneously actuated. Alternatively, the retraction unitmay be configured to first retract the core and then retract the sheath.

Devices other than a set screw may releasably hold the cable 50 tohandpiece 52. For example, in one version of the invention a cammingdevice may hold the cable 50 in place. In these versions of theinvention, the camming device may normally hold the cable to thehandpiece 52. The rearward movement of the proximal slide 64 may movethe cam from the locked state to the unlocked state. This transitioningof the cam unlocks the grip the cam imposes on the cable. A benefit ofthis version of the invention is that it eliminates the need for thepractitioner to have to adjust a screw or similar locking component whenit is time to withdraw the cable.

The other components of system 50 of this invention may also bedifferent. For example, the guidewire of this invention may be providedwith one or more steering cables. This would allow the guidewire to beselectively steered past obstructions between where the guidewire isintroduced and the target tissue. Likewise, in some versions of theinvention, the dilator and insertion sleeve may have sufficient lengthso as to extend over the whole of the guidewire. Using the components ofthis version of the invention, once the guidewire is properlypositioned, the inserter is then moved distally forward to extend oversubstantially all of the guidewire. The inserter thus extends over thetarget tissue. The guidewire and dilator are then removed. The sheathand/or core are then advanced through the inserter sleeve to the sectionof the sleeve over or adjacent to the target tissue. The introducersleeve is then removed from the patient. This type of introducer systemcould be useful for inserting paddle type arrays. These versions are theinvention are useful when it is desired to provide a path that isunobstructed as possible from the portal through which the electrodearray is introduced to the location over the target tissue where theelectrode array is to be deployed.

Also, while the components of this invention are designed to facilitatethe percutaneously insertion of electrode arrays, the components of thisinvention may find utility in procedures in which large incisions aremade in order to implant and deploy an electrode array.

The stated dimensions, unless recited in the claims, are for purposes ofexample only.

Therefore it is an object of the appended claims to cover all suchmodifications and variations that come within the true spirit and scopeof this invention.

What is claimed is:
 1. An assembly for percutaneously inserting animplantable medical device, the assembly including: a handpiece shapedto be held in a single hand; a sheath, said sheath having a distalportion in which the implantable medical device is disposed and aproximal portion that extends rearwardly from the distal portion so theproximal portion can extend out of the living being in which the sheathis inserted, the proximal portion of said sheath being moveably attachedto said handpiece so that the sheath can be retracted away from themedical device; at least one steering cable is connected to either tosaid sheath or the medical device or said sheath for steering the deviceand said sheath with the device is disposed in said sheath, saidsteering cable extending to said handpiece; a steering unit attached tosaid handpiece, wherein said at least one steering cable is attached tosaid steering unit and said steering unit selectively controls said atleast one steering cable and said steering unit has a manually actuatedcontrol member that is manipulated to control said at least one steeringcable, said control member being positioned on said handpiece to bemanipulated by the hand holding said handpiece; and a first retractionunit attached to said handpiece, wherein said sheath is attached to saidretraction unit so that the actuation of said first retraction unitresults in the retraction of said sheath proximally away from theimplantable medical device, said first retraction unit having a manuallyactuated control member that actuates said first retraction unit, saidcontrol member being positioned on said handpiece to be manipulated bythe hand holding said handpiece.
 2. The assembly of claim 1, furtherincluding: a core for supporting the implantable medical device (30)wherein the medical device and the core are encased in the sheath; andwherein, a second retraction unit is disposed in said handpiece and saidcore is connected to said second retraction unit, said second retractionunit configured to, when actuated, retract said core proximally awayfrom the implantable device, said second retraction unit having amanually actuated control member that actuates said second retractionunit, said control member being positioned on said handpiece to bemanipulated by the hand holding said handpiece.
 3. The assembly of claim2, wherein said first retraction unit and said second retraction unitare collectively configured so that a single manually actuated controlmember actuates both said retraction units.
 4. The assembly of claim 3,wherein said first retraction unit and said second retraction unit arecollectively configured so that said second retraction unit is notactuated after said first retraction unit initially at least partiallyretracts the sheath away from the medical device.
 5. The assembly ofclaim 2, wherein said first and second retraction units are collectivelyconfigured so that the actuation of one of said retraction units resultsin the simultaneous actuation of the other one of the retraction units.6. The assembly of claim 2, wherein: said first retraction unit is afirst slide that is moveably disposed in said handpiece; and said secondretraction unit is a second slide that is moveably disposed in saidhandpiece.
 7. The assembly of claim 1, wherein said first retractionunit is a slide that is moveably disposed in said handpiece.
 8. Theassembly of claim 7 wherein said at least one steering cable andcomponents of said steering unit are attached to said slide.
 9. Theassembly of claim 1, wherein: plural said steering cables are connectedto said sheath or the medical device; and said steering unit is able toselectively tension the plural said steering cables.
 10. The assembly ofclaim 9, wherein said steering unit includes a single said controlmember that is selectively manipulated to selectively tension the pluralsteering cables.
 11. An assembly for percutaneously inserting animplantable medical device, the assembly including: a core forsupporting the implantable medical device; a sheath, said sheath havinga distal portion in which the implantable medical device and core aredisposed and a proximal portion that extends rearwardly from the distalportion end so the proximal portion can extend out of the living beingin which the sheath is inserted, the proximal portion of said sheathbeing moveably attached to said handpiece so that the sheath can beretractable away from the medical device; at least one steering cable isconnected to either to said sheath or the medical device or said sheathfor steering the device and said sheath with the device is disposed insaid sheath, said steering cable extending to said handpiece; ahandpiece, said handpiece shaped to be held in a single hand, whereinthe proximal end of said sheath and said core are each connected to saidhandpiece; a first retraction unit attached to said handpiece, whereinsaid sheath is attached to said retraction unit so that the actuation ofsaid first retraction unit results in the retraction of said sheathproximally away from the implantable medical device, said firstretraction unit having a manually actuated control member that actuatessaid first retraction unit, said control member being positioned on saidhandpiece to be manipulated by the hand holding said handpiece; and asecond retraction unit attached to said handpiece, wherein said core isattached to said retraction unit so that the actuation of said secondretraction unit results in the retraction of said core proximally awayfrom the implantable medical device, said second retraction unit havinga manually actuated control member that actuates said second retractionunit, said control member being positioned on said handpiece to bemanipulated by the hand holding said handpiece.
 12. The assembly ofclaim 11, wherein said first retraction unit and said second retractionunit are collectively configured so that a single manually actuatedcontrol member actuates both said retraction units.
 13. The assembly ofclaim 11, wherein said first retraction unit and said second retractionunit are collectively configured so that said second retraction unit isnot actuated after said first retraction unit initially at leastpartially retracts the sheath away from the medical device.
 14. Theassembly of claim 13, wherein said first retraction unit and said secondretraction unit are collectively configured so that a single manuallyactuated control member actuates both said retraction units.
 15. Theassembly of claim 11, wherein said first and second retraction units arecollectively configured so that the actuation of one of said retractionunits results in the simultaneous actuation of the other one of theretraction units.
 16. The assembly of claim 11, wherein at least one ofsaid retraction units is a slide that is moveably disposed in saidhandpiece.
 17. The assembly of claim 11, wherein: said first retractionunit is a first slide that is moveably disposed in said handpiece; andsaid second retraction unit is a second slide that is moveably disposedin said handpiece.
 18. The assembly of claim 11, wherein: at least onesteering cable is connected to either to said sheath or the medicaldevice or said sheath for steering the device and said sheath with thedevice is disposed in said sheath and said steering cable extending tosaid handpiece; and a steering unit is attached to said handpiece,wherein said at least one steering cable is attached to said steeringunit and said steering unit selectively controls said at least onesteering cable and said steering unit has a manually actuated controlmember that is manipulated to control said at least one steering cable,said control member being positioned on said handpiece to be manipulatedby the hand holding said handpiece.
 19. An assembly for percutaneouslyinserting an implantable medical device, the assembly including: asheath, said sheath having a distal portion in which the implantablemedical device is disposed and a proximal portion that extendsrearwardly from the distal portion so the proximal portion can extendout of the living being in which the sheath is inserted; at least onesteering cable fitted to said sheath; a handpiece shaped to be held inthe hand, wherein the proximal end of said sheath and said steeringcable extend to said handpiece; a slide moveably disposed in saidhandpiece, wherein: the proximal end of said sheath and said at leastone steering cable are connected in said slide; and a control member isconnected to said slide for moveably displacing said slide within saidhandpiece so that the displacement of said slide results in theretraction of said sheath away from the implantable medical device; anda steering unit attached to said handpiece, wherein: said at least onesteering cable is attached to said steering unit and said steering unitselectively controls said at least one steering cable; said steeringunit has a manually actuated control member that is manipulated tocontrol said at least one steering cable, said control member beingpositioned on said handpiece to be manipulated by the hand holding saidhandpiece; and said steering unit has at least one additional componentthat is mounted to said slide.
 20. The assembly of claim 19, wherein:said handpiece includes a housing; and said steering unit includes acontrol member that is mounted to said handpiece housing, said steeringunit control member configured to engage the said steering unitcomponent that is mounted to said slide.
 21. The assembly of claim 19,wherein: said steering unit is configured to impose a force on said atleast one steering cable; and a tensioner is disposed in said housing,said at least one steering cable is attached to said tensioner and saidtensioner is configured to limit the amount of force said steering unitplaces on said at least one steering cable.
 22. The assembly of claim21, wherein said tensioner is mounted to said slide to move with saidslide.
 23. The assembly of claim 19, wherein a plurality of saidsteering cables extend from said sheath to said slide.
 24. The assemblyof claim 19, wherein said control member connected to said slide ispivotally connected to said handpiece.
 25. The assembly of claim 19,wherein said slide and said control member connected to said slide areconfigured to: move said slide in a first direction within saidhandpiece to cause the retraction of said sheath away from theimplantable medical device: and after said slide is moved in the firstdirection, inhibit movement of said slide in a second direction oppositethe first direction.
 26. The assembly of claim 19, further including: acore disposed in said sheath for supporting the implantable medicaldevice, said core being connected to said handpiece; and a coreretraction assembly disposed in said handpiece to which said core isattached, said core retraction assembly configured to, when actuated,retract said core away from the implantable medical device, wherein saidslide and said core retraction device are at least partially able to beactuated independently of each other.